CHEMISTRY COMMUNITY

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Yes, at equilibrium, the forward and reverse reaction rates are equal which is the reason there is no change in the concentration of the products and the reactants. Also, the instantaneous rate is a more accurate measurement of the rates of the reactants and the products as it takes the smallest tim...

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For a first-order reaction, the half-life is equal to ln2/kr which means that when kr, the rate constant, increases, the half-life will decrease since kr is in the denominator and they are inversely proportional. The same proportion is true for the zeroth and second half-lives as they have kr in the...

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Termolecular reactions occur when the formation of the product depends on the collision between three reactants. For example, A + A + B --> C.

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The unit for k for a zeroth-order reaction is moles per liter per second since the power of the concentration of the reactant is zero and the rate value must have the rate in moles per liter per second. For a first-order reaction, the rate is equal to the rate constant x the concentration of the rea...

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The forward and reverse reaction proceed by the same mechanism which means that if the forward reaction is facilitated, the reverse is also facilitated.

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A zeroth-order reaction has a rate that does not depend on the concentration of any of the reactants but takes place at the same rate no matter the concentration of the reactant. For example, the reaction takes place at the same rate when reactant A's concentration is 1/2 of its initial concentratio...

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A zeroth-order reaction has a rate that does not depend on the concentration of the reactant. This is commonly observed in enzyme-catalyzed reactions when the enzyme is saturated with the substrate and increasing the substrate has no effect on the rate of the reaction since there are no more enzymes...

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The rate constant shows the relation between the concentration of a reactant and the rate of a reaction. The rate of a reaction depends on the concentration of the reactant with a proportionality constant of the rate constant. Because the proportionality between the rate of the reaction and the conc...

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The rate-limiting step is the slowest step in a reaction. The slowest step determines the overall rate of the reaction since the completion of the reaction depends on that step. For example, if you have a three-step reaction where the first step has a rate of 80 moles per liter per second, the secon...

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As the temperature increases, the kinetic energy of the particles in the reaction increases. This causes more collisions to occur between the reactants which cause the reaction to proceed at a faster rate and the activation energy to be lowered which is the minimum amount of energy required to drive...

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The instantaneous rate decreases as the reaction proceeds because the reactants are consumed and less amount of reactant is left in the reaction which causes the rate of the reaction to decrease since the number of collisions between the reactants decreases and the change in the reactant concentrati...

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Yes. To find the slope of the tangent line you would have to either take a very small time step and divide the difference of the variables at those two time values and divide them by the time step. Another way to do it would be to take the limit of the difference of the variables at two times divide...

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I think the electrons can only flow from the anode to the cathode since oxidation always takes place in the anode and reduction in the cathode. The salt bridge exists to counteract the charge imbalance created by the one-way flow of the electrons. If the electrons could flow both ways, there would b...

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The differential rate law provides the relationship between the rate of a reaction and the concentration of the reactant. This determines the dependence of a reaction on the concentration of a specific reactant by giving the contribution of each reactant to the overall rate of the reaction.

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Since the electron flow between the cathode and the anode depends partly on the charge difference between the two solutions in the way that a slightly positive or negative charge may attract or repel the electron and prevent the flow of the electron from the anode to the cathode. This would result i...

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If a species is being oxidized, this means it had lost an electron which has to be donated to another species. Because an electron lost by a species has to be gained by another species. Therefore, a species has to be reduced while the other is being oxidized. The species that is oxidized is the caus...

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The cell potential does not depend on the number of moles of an element. For example, if we have A2+ + 2e --> A, the cell potential does not change when the number of moles of A increases. For example, multiplying the equation with 2, 2A2+ + 4e --> 2A still has the same cell potential. However, when...

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The cell potential does not depend on the number of moles of an element. For example, if we have A2+ + 2e --> A, the cell potential does not change when the number of moles of A increases. For example, multiplying the equation with 2, 2A2+ + 4e --> 2A still has the same cell potential. However, when...

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Oxidation is the loss of electrons. In order to determine which species has lost an electron, you need to know the oxidation states of the elements you are dealing with. For example, oxygen has an oxidation state of -2 in H2O whereas hydrogen has an oxidation state of -1. By looking at the oxidation...

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The work done on a system is always positive since energy is spent on the system and the system gains the energy spent whereas the work done by the system is negative since the system spends energy and it is lost to its surroundings which gain this energy.

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It always goes from the anode to the cathode in a Galvanic cell since the anode is negatively charged and the cathode is positively charged and will attract the electrons from the anode. However, in an electrolytic cell, the cathode and anode do not have the same charges, regardless the electron sti...

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According to the laws of thermodynamics, the entropy of a system always tends to increase. This is because when entropy increases, the number of states a particle can be found in increases which removes the constrains on that particle that stores potential energy. Imagine a gas in a small container....

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A cathode is a positively charged electrode which the electrons flows toward because of its positive charge. An anode is a negatively charged electrode which the electron flows from because of its negative charge. These hold true for cathodes and anodes for a Galvanic cell. Oxidation is the loss of ...

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For Part A, you have to add up three different delta S values to find the total change of entropy in the system. This includes deltaS for H2 container expansion, deltaS of Krypton gas for container expansion, and deltaS based on temperature change. Since entropy is a state function, this allows us ...

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When a reaction is exothermic, the delta G is negative. In order for delta G to be negative, the change in enthalpy must be smaller and the change in entropy must be greater. This is because the term delta H does not have a negative sign in front of it which means that if it is increased, delta G in...

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If you have a delta G that is negative which means that the reaction is spontaneous, then the reaction does not need energy to proceed. In other words, it will occur on its own without any external intervention. Because this reaction occurs spontaneously without the input of energy, this means that ...

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Work is not a state property because the work you have done does not depend on the difference between the final state and the initial state. For example, you may go up a hill along a straight path and you may also go up the hill in a rocky path that increases the distance between the ground and the ...

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An acid is weak if it does not dissociate fully. When an acid dissociates only partially, the concentration of the hydrogen atoms released into the surrounding solution is less than a strong acid. Because the concentration of the hydrogen atoms is less than it would be if it dissociated fully, the p...

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When delta is smaller than zero, the reaction is spontaneous, meaning that it will occur without energy input. We knew that delta G must have been spontaneous, but we did not know the exact temperature at which it would turn spontaneous. The critical point here is delta G = 0 since it is the point a...

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q = C delta T gives the heat capacity whereas q = m C delta T gives the specific heat per 1 gram of the substance since there is multiplication with the grams of the substance.

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K is the constant that gives the ratio of equilibrium concentrations of a reaction whereas Q gives the ratio of the concentration of the products to the reactants at any given point in time as the reaction is occurring. They are both calculated the same way, however, Q can be calculated at any point...

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The Boltzmann equation gives the relationship between the entropy of a system and the number of different ways or microstates that the system can be arranged on energy levels which is w.

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When a reaction is spontaneous, it does not require a net input of energy to occur. For example, the melting of ice occurs spontaneously, or the diffusion of air does not require an effort whereas performing these reactions in the reverse direction would require an effort. When a reaction is spontan...

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When the reaction is reversed, your initial products will become the new reactants and initial reactants will become new products so if A + B --> C where the enthalpy of the product C is greater than the reactants, then the reverse will be C --> A + B. Since enthalpy is calculated as the enthalpy of...

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Volume and pressure are inversely related so when the pressure increases, the volume decreases, and when pressure decreases, volume increases. For example, when the volume of a container is decreased, the same moles of gas will be contained in a smaller volume, thus increasing the pressure they appl...

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Since delta H is equal to the energy of products - reactants, if delta H is positive, the energy of the products will be larger than the energy of the reactants meaning that there is an input of energy and the reaction is endothermic. If the energy of the reactants is greater than the energy of the ...

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I think it depends on the units of the elements. Usually, the temperature is given in degrees Celsius and so is the specific heat or heat capacity. So you do not have to convert it to kelvin.

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The breaking of bonds always requires energy. However, the overall heat change of the system also takes into account other factors. For instance, the breaking of the bond between two phosphates in the decomposition of ATP into ADP and inorganic phosphate requires an energy input and is therefore end...

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Heat is not a state function because it does not depend on the initial and final conditions of a system. For example, enthalpy which describes the change in the heat of the system depends on the difference between the final and initial state of the system. Therefore, as long as the final and initial...

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Adding a catalyst does not change the equilibrium because it is a kinetic property that favors both the forward and reverse reactions at the same rate and does not change the coefficients. The system may reach equilibrium faster but the equilibrium concentrations will not change. For example, reacti...

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At constant temperature, changing the concentration, pressure or volume will not change the K value. This is because the system will shift to counteract the stress and balance itself once again. For example if you decrease the amount of products, the numerator of K will go down but it will be counte...

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I think temperature changes the equilibrium constant because it favors either endothermic or exothermic reactions. For example, if we have a reaction A + B --> C, and the forward reaction is endothermic, changing the temperature will favor the forward reaction. As the equilibrium constant indicates ...

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I think you can tell by looking at the hear input of output if it is given, or you could look at whether there is bond formation or the breakage of bonds which would indicate whether energy is needed or released. By looking at the energy of the products and the reactants you can determine that the r...

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The coefficients are taken into account when calculating the concentration of the reactants and the products. Once you have done that, I don't think you need to consider the coefficients again. For example, if you have calculated that there was x amount of product at equilibrium and y amount initial...

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Le Chatelier's Principle states that when there is a stress that is a applied to a system such as temperature, pressure, or concentration changes, the system will counteract this stress and balance itself again. For example, if I increase the concentration of the reactants, the concentration of the ...

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The product is favored when the reaction is endothermic because the forward reaction requires the input of energy and that required energy is provided excessively by the increase in temperature. In endothermic reactions, the heat is on the reactants side since it is an input. Therefore, when the tem...

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Acids and bases that completely ionize dissociate completely and release hydrogen or hydroxide ions to the solution whose molarities are equal to the molarity of the acid (by taking into account the stoichiometric coefficients). This means that the acid or the base has completely given off its hydro...

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I think the acid strength increases as the oxidation number of the central atom increases since the central atom will be more electronegative and pull the electrons away from the surrounding atoms which results in a weaker bond between the central and surrounding atom that makes it easier for the su...

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I think it depends on the case and the overall heat change of the system. But since, energy in the form of heat is required to break the bonds, it is most likely that the reaction will be endothermic and require energy. This cannot be generalized though. For example, the dissociation of ATP to ADP a...

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I think it depends on the case and the overall heat change of the system.

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When we consider a change in pressure, we assume a constant concentration of the reactants even though the volume has changed. When you increase the pressure, the volume decreases, and so there will be the same amount of reactants as there were in the first place but the volume they occupy has decre...

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The reaction quotient is used to calculate the ratio of the reactant and product concentrations at any point as the reaction takes place. When the reaction quotient equals the equilibrium constant k, the reaction reaches equilibrium. Thus, the reaction quotient is used to calculate whether the forwa...

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Solids and liquids are excluded from the equilibrium constant expression because their concentration equals their density divided by their molar mass. Since the density of a pure solid or liquid is constant regardless of how much solid or liquid is present, their concentrations stay constant through...

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The K value is the equilibrium constant which is calculated by the concentration of the products divided by the concentration of the reactants at equilibrium. When the K value is large, this means that then the concentration of the products which is in the numerator is significantly larger than the ...

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You can also figure out the oxidation number of atoms by looking at the oxidation number of other atoms in a molecule. For example, we know that the oxidation number of oxygen is -2 so we can find the oxidation number of another atom that is bound to oxygen by making the overall oxidation number equ...

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Yes, when determining points of hydrogen bonding, lone pairs are also considered if it is on an N, O, or F as well as the hydrogens since the hydrogens will form a bond with those electronegative atoms.

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The ability of an ion to change the pH of the solution depends on what it is a conjugate of. If you have a strong acid and a weak base, the base will be protonated and the resulting compound will have be a strong conjugate acid so the salt solution will be acidic. For example, if we titrate a strong...

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Bronsted acids and bases refer to the substances that are considered as acids and bases based on the Bronsted definition which means that a substance that is considered an acid would be the proton donor and a substance that is considered a base would be the proton acceptor. Conjugate acids and bases...

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Because Bronsted acids are defined to be the molecules to that donate a proton (H atom), NH4+ would be the Bronsted acid here as it is the one that donated a proton to HCO3- and became NH3. Lewis acids are defined to be the lone pair acceptors so NH4+ would be considered a Lewis acid since it is pos...

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There are two definitions for both acids and bases. These are Bronsted acid and bases and Lewis acid and bases, both of which define an acid and a base in a different way. A Bronsted acid is a substance that donates hydrogen ions to the solution it is found in, whereas a Bronsted base is a substance...

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Amphoteric molecules have the characteristics of both acids and bases. This means that they are able to act as acids or bases depending on the circumstances and what they are reacting with. Amphoteric substances are usually created by metalloids which also have the characteristics of both metals and...

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The strength of an acid or base is determined by its ability to dissociate in water. A strong acid would completely dissociate in the water, yielding a hydronium ion of the same concentration as the concentration of the acid itself. For example, HCl would dissociate completely into hydrogen and chlo...

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Hydrogen bonding sites are where hydrogen bonding can occur. This includes hydrogen atoms that are bound to electronegative atoms like F, N, or O. A hydrogen bound to one of these elements would be a potential site for hydrogen bonding as well as the nitrogen, fluorine, and oxygen atoms bound to hyd...

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Yes. You need to know the difference between cis and transplatin and how one can play an important biological role while the other cannot despite the fact that they both have the same composition. Cis-platin has its two chlorine atoms on one side, meaning that they are not on opposite sides. This br...

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There is a difference between the electron configuration of a molecule and the shape of the molecule. While the electron configuration takes lone pairs into accounts as well due to the fact that they are regions of electron density as well, however, the shape of the molecule solely depends on the po...

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Hybridized orbitals have an energy between the orbitals of which they are composed. So sp3 has 3 hybridized orbitals of equal character that have an energy in between the energy of s orbital and the energy of p orbital. I do not think that the hybridized orbitals have any energy difference among eac...

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The best way to determine ionic and covalent bonds would be looking at electronegativity difference between the atoms in the bond and also the polarizability of the atoms which will contribute to the covalent and ionic bond character of the bond. When the polarizability of the anion increases, and t...

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Sigma bonds overlap end-to-end to form a bond, whereas pi bonds form by overlapping side-by-side with each other. A significant difference is that sigma bonds allow rotation of atoms, whereas the pi bonds break if one of the atom rotates. Also, sigma bonds are more stable than pi bonds and form befo...

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I think the bond angles increases from sp3 to sp2 because number of hybrid orbitals = number of regions of electron density. So, if you have sp3 you have 4 regions of electron density as you have 4 hydrid orbitals, whereas when you have sp2 you have 3 regions of electron density as you have 3 hydrid...

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London dispersion forces or induced dipole-induced dipole interactions are universal because this type of interaction occurs between any two molecules due to the fluctuating electron densities of the individual atoms of a molecule which results in temporarily positively charged and negatively charge...

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Knowing the exact location of lone pairs would be difficult but one guideline would be balancing the distance between lone pairs and the bonding electrons since they will all repel each other as they are regions of electron density. Lone pair-lone pair repulsion will be the greatest, the lone pair-b...

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Hydrogen bonds occur between the hydrogen that is bound to an electronegative atom like fluorine, nitrogen, oxygen, and fluorine, nitrogen, or oxygen that are partially charged. For example, hydrogen bonding occurs between the water molecules between partially negatively charged oxygen and partially...

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Rod-shaped molecules have higher boiling points than spherical molecules because of the heightened interactions between the molecules. Boiling points depend on the strength of intermolecular forces. When a molecule is more linear as in the case of rod-shaped molecules, it will have a larger surface ...

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Induced dipole-induced dipole interactions are a result of fluctuating electron densities. For example, if you put two nonpolar molecules together that do not contain any dipoles in their bonds, there would be no interaction between the molecules that was due to a difference in charges such as parti...

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The reason lies in the electron configuration of the oxygen atom. Oxygen has 6 valence electrons in its n = 2 shell. 2 of these electrons will occupy the 2s subshell while the remaining 4 will occupy the 2p subshell. Because 2p subshell has 3 orbitals, the oxygen atom will have 1 pair of electrons i...

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The De Broglie equation only applies to particles that have a resting mass and therefore cannot be applied to light. Light is just electromagnetic radiation, and photons are discrete packets of energy that have no mass. To find the wavelength of light, you will need to use the c = lambda x frequency...

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The polarizability of an anion is dependent on the number of electrons it has which is also dependent on the neutral state of the atom and the nuclear charge. The more electrons an atom has, the greater its electron cloud and the more electrons that are further away from the nucleus which may be att...

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Subshells are 1s, 2p, ... Orbitals are px, py, pz, dx, ... So, for example, the px orbital can accommodate up to 2 electrons. Each orbital can be occupied by a maximum of 2 electrons each with opposite spin. For n = 2 There are 2 subshells (2s, 2p), and a total of four orbitals (one s, and 3 p orbit...

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Yes, they have to follow the octet rule because they cannot have an expanded octet since they are in the second period and do not have the shell n=3. Therefore, they do not possess a d orbital which can hold up to 10 electrons and therefore allow the atom to expand its octet. Atoms in the first and ...

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When lookıng at a trend, to determine whether the noble gases are included, you should consider the properties of noble gases. Since the atomic radius is a general concept it can be applied to noble gases as well. Electronegativity does not apply because it is defined as the pull the nucleus of an a...

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The answers would not change for H because the electron would still move to a higher energy level, and move to a different orbital. This change would result in the expansion of the atom which would cause the radius of the atom to increase in both scenarios. Therefore, the energy of the electron has ...

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I don't think there is a clear relationship between polarizability and electronegativity since polarizability depends on the type of atoms involved in the bonding as well. Roughly, we could say that as the electronegativity increases, the pulling of electron by an atom increases and therefore it has...

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The 3d subshell is high in energy compared to the 4s subshell when the 4s subshell is unfilled with electrons. Once the 4s subshell has been filled, however, the 4s subshell will become higher in energy, and the next subshell to be filled will be the 3d. Even though 3d subshell had higher energy ini...

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Electron affinity is the desire of an atom to receive an electron or the energy that is released when an electron is added to an atom. It increases from left to right and bottom to top, same as ionization energy, because the atomic radius decreases which increases the electrostatic interactions of t...

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Metalloids have a characteristic diagonal pattern in the periodic table, so if you start with boron and follow a diagonal pattern until you reach a noble gas, specifically Og, and then add Sb and Ge which are the only ones left out, you can easily find out the metalloids. The elements to the right o...

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The 4s orbital has lower energy than the 3d orbital when it is unoccupied by electrons. Because electrons always fill the lower energy level first, 4s orbital will be filled before 3d. After 4s orbital has been occupied by electrons, the 3d orbital will be filled which will shield the 4s electrons f...

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As far as we know, nothing can be faster than light, so if the speed of an electron, proton, or a neutron is faster than speed of light, there must have been an error in the calculations. The reason for nothing being greater than the speed of light is due to the absolute space-time in physics which ...

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I think you cannot calculate the E = hc/lambda equation because it is defined for light. The calculations we did always assigned the speed of light to c. In that case, you could use it for calculating the energy of a photon but cannot use it for any other particle. The reason we use lambda = h/mv is...

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Radio waves have the lowest frequency, infrared radiation has lower frequency and longer wavelength than visible light and is usually emitted in the form of heat so it is has lower energy, visible light can be thought of as a transition spectrum between the infrared and the ultraviolet radiation, ha...

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I think the extent of the energy change means the perturbation caused to the electrical field due to the oscillations of the electromagnetic wave. The extent of the change is proportional to the energy of the wave. The higher the energy, the greater the effect of the wave on the field, since greater...

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The intensity of a wave is defined by the number of photons it contains. The energy of the wave, however, refers to its frequency as the energy of the photons only increases with an increase in frequency. For example, when the intensity of the wave was increased in the photoelectric experiment for l...

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Frequency is the total energy of a single photon in the wave model since as we have seen in the photoelectric experiments, there is a certain amount of energy needed to remove electrons from the surface of a metal, called the threshold energy. The energy of the photon must be equal to or greater tha...

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Hi, so I asked the same question today, and Prof. Lavelle told me that the double derivate of sin would indeed be -sin, but the double derivate of theta is also negative so the negative signs cancel each other out, and therefore the final product is positive.

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Calcium has a +2 charge whereas hydroxide has a -1 charge. Because compounds are always neutral, there must be enough of both elements to cancel out the charges. This means that there should be a total of -2 charge for hydroxide to cancel out the +2 charge of calcium. Therefore, there must be 2 hydr...

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Hi, we know that E(photon) - Work function = Ek(electron) We know that the work function is 7.22x10^-19J. We also know that the wavelength of the incoming light is 194 nm which is 194 x 10^-9 m. To calculate the energy of the photon, we need to use the equation E = hv. So we need to know the frequen...

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Molecules can be represented in various ways. For example, you could write the formula for the molecule like H2O, or you could draw its molecular structure like H-O-H. These are different ways of representing molecules. Writing formulas from molecular structures means writing the formula of the mole...

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So, the question states that there are two reactions occurring. The first reaction occurs between P4 and O2 to yield P4O6. If enough oxygen is present, the oxygen can react further with this oxide to produce P4O10. First, you need to determine the limiting reactant for the first equation. It states ...

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The photoelectric experiment led to the rise of the equation: E=hv. This is because the photoelectric effect showed that it isn't the intensity of the light that determines the energy of the individual photons but the frequency of the light since no electrons were removed by long-wavelength or in ot...

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The theoretical yield is what you would obtain in perfect conditions where the reactants are pure. However, during an experiment, side reactions could occur, the reactants could stick to the walls of the container, decreasing the amount of reactants that are reacting, or impurities in the container ...

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If the question does not specify with which compound iron (III) oxide was reduced, I don't think there is any way for you to write a balanced equation as the iron (III) oxide could react with a wide variety of compounds to gain an electron and become reduced. The only thing you could do would be to ...

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