CHEMISTRY COMMUNITY

Talia Dini - 3I

Oxidation which occurs at the anode of a galvanic cell is the loss of electrons. Reduction which occurs at the cathode of a galvanic cell is the gain of electrons.

Talia Dini - 3I

Yes! Oxidation would occur at the anode and reduction would occur at the cathode.

Talia Dini - 3I

Yes, you would flip the sign of the cell potential when you reverse an equation.

Talia Dini - 3I

A catalyst increases the speed and lowers the activation energy of the forward and reverse reaction. Hope this helps!

Talia Dini - 3I

Yes, that would be correct! K would be equal to kforward/kreverse.

Talia Dini - 3I

A salt bridge prevents the build-up of charges. This occurs by anions traveling to the anode and cations traveling to the cathode.

Talia Dini - 3I

Hi! You would add Pt(s) at the end of a cell diagram if a conducting solid is not present.

Talia Dini - 3I

Could someone please walk me through how they solved this problem? I'd greatly appreciate it! 6.73 The “aluminum–air fuel cell” is used as a reserve battery in remote locations. In this cell, aluminum reacts with the oxygen in air in basic solution. (a) Write the oxidation and reduction half-reactio...

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Hi! Could someone please explain to me how they went about solving this problem?

6.65 What range (in volts) does a voltmeter need to have to measure pH in the range of 1 to 14 at 25 degrees C if the voltage is zero when pH=7?

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I'd greatly appreciate it if someone could please explain how they solved this problem!

6.57 Use the data in Appendix 2B and the fact that, for the half-reaction F2(g)+ 2H+(aq) +2e- --> 2HF(aq), E8 = 3.03 V, to calculate the value of Ka for HF.

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Could someone please walk me through how they solved this problem? I am having some difficulty with it. 6.53 (a) If you were to construct a concentration cell in which one half-cell contains 1.0 M CrCl3(aq) and the other half-cell contains 0.0010 M CrCl3(aq), and both electrodes were chromium, at wh...

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Hi, could someone please explain to me how they went about solving this problem?

Talia Dini - 3I

Could some please explain how they solved this problem? I'd greatly appreciate it! 6N.9 A tin electrode in 0.015 M Sn(NO3)2(aq) is connected to a hydrogen electrode in which the pressure of H2 is 1.0 bar. If the cell potential is 0.061 V at 25 degrees C, what is the pH of the electrolyte at the hydr...

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Hi! I'm having some trouble figuring out part b of this problem, could someone please walk me through it?

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The oxidizing agent oxidizes another molecule so it is being reduced and gaining electrons. The reducing agent is reducing another molecule so it is being oxidized and losing electrons.

Talia Dini - 3I

I'd greatly appreciate it if someone could walk me through this problem! I'm having some trouble figuring it out.

Talia Dini - 3I

Could someone please explain how they solved this problem? I'd greatly appreciate it!

Talia Dini - 3I

Hi! I'm having some trouble figuring out part d of this question. Could someone please walk me through it?

6L.3 Write the half-reactions and the balanced equation for the cell reaction for each of the following galvanic cells:
(d) Pt(s) I O2(g) I H+(aq) II OH-(aq) I O2(g) I Pt(s)

Talia Dini - 3I

Yes! The anode has to be on the left of the cell diagram and the cathode has to be on the right of the cell diagram.

Talia Dini - 3I

n would be representative of the number of moles of electrons that are transferred once an equation is balanced. Hope this helps!

Talia Dini - 3I

Yes! The oxidating agent would be the molecule that is being reduced and the reducing agent would be the molecule that is being oxidized.

Talia Dini - 3I

Delta H will be equal to 0 under constant pressure conditions. Hope this helps!

Talia Dini - 3I

If work is done by the system then the value for work will be negative. If work is done on the system then the value for work will be positive.

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Adiabatic means that heat is not exchanged between the system and the surroundings.

Talia Dini - 3I

In an isolated system, both matter and energy can not be exchanged. Since work and heat are forms of energy exchanges, they would equal 0. Hope this helps!

Talia Dini - 3I

In an open system, matter and energy can be exchanged. In a closed system, only energy can be exchanged. In an isolated, both matter and energy can not be exchanged.

Talia Dini - 3I

If you are given the value of pressure in kPa, you can convert it into atm using the conversion 1 atm = 101.325 kPa. You can use the gas constant R = 8.206 *10^-2 L*atm*K^-1*mol^-1 so that the units would cancel out.

Talia Dini - 3I

Yes, as long as the lid is on, a thermal mug would be an example of an isolated system because energy and matter can not be exchanged.

Talia Dini - 3I

Hi! I'd really appreciate it if someone could walk me through how they solved this problem! 4I.9 Initially an ideal gas at 323K occupies 1.67L at 4.95atm. The gas is allowed to expand to 7.33 L by two pathways: (a) isothermal, reversible expansion; (b) isothermal, irreversible free expansion. Calcul...

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Hi! Could someone please walk me through how they solved this problem? 4F.1 A human body generates heat at the rate of about 100. W(1W = 1J*s^-1). (a) At what rate does your body heat generate entropy in your surroundings, taken to be at 20. 8C? (b) How much entropy do you generate each day? (c) Wou...

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I'm having some trouble figuring out this problem, could someone please explain how they solved it? 4.59 A technique used to overcome the unfavorable thermodynamics of one reaction is to “couple” that reaction to another process that is thermodynamically favored. For instance, the dehydrogenation of...

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Could someone please explain to me how they went about solving this problem? 4.43 Hydrogen burns in an atmosphere of bromine gas to give hydrogen bromide gas. (a) What is the standard Gibbs free energy of the reaction H2(g) 1 Br2(g) S 2 HBr(g) at 298 K? (b) If 120. mL of H2 gas at SATP combines with...

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Hi! I'd greatly appreciate it if someone could explain how they solved this problem!

4I.5 Suppose that 50.0 g of water at 20.0 8C is mixed with 65.0 g of water at 50.0 8C at constant atmospheric pressure in a thermally insulated vessel. Calculate DS and DStot for the process.

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Could someone please walk me through how they solved this problem? I'd greatly appreciate it! 4I.3 The standard entropy of vaporization of benzene is approximately 85 J?K21 mol21 at its boiling point. (a) Estimate the standard enthalpy of vaporization of benzene at its boiling point of 80. 8C. (b) W...

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I'm having some trouble solving this problem, could someone please walk me through it? 4F.7 Assuming that the heat capacity of an ideal gas is independent of temperature, calculate the entropy change associated with raising the temperature of 1.00 mol of ideal gas atoms reversibly from 37.6 8C to 15...

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I'd really appreciate it if someone could please explain how they solved this problem! 4.23 In a microwave oven, radiation is absorbed by water in the food and the food is heated. How many photons of radiation of wavelength 4.50 mm are required to heat 350. g of water from 25.0 8C to 100.0 8C, assum...

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Hi! Could someone please explain how they solved this problem? 4.15 Hydrochloric acid oxidizes zinc metal in a reaction that produces hydrogen gas and chloride ions. A piece of zinc metal of mass 8.5 g is dropped into an apparatus containing 800.0 mL of 0.500 m HCl(aq). If the initial temperature of...

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Could someone please explain how they went about solving this problem? I'd really appreciate it! 4D.3 The reaction of 1.40 g of carbon monoxide with excess water vapor to produce carbon dioxide and hydrogen gases in a bomb calorimeter causes the temperature of the calorimeter assembly to rise from 2...

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Hi! Could someone please walk me through how they solved part b of this problem? 4B.13 Calculate the work for each of the following processes beginning with a gas sample in a piston assembly with T 5 305 K, P 5 1.79 atm, and V 5 4.29 L: (a) irreversible expansion against a constant external pressure...

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I'm having some problem figuring out this problem, could someone please explain how they solved it? 4A.13 A constant-volume calorimeter was calibrated by carrying out a reaction known to release 3.50 kJ of heat in 0.200 L of solution in the calorimeter (q 5 23.50 kJ), resulting in a temperature rise...

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Hi! Could someone please walk me through how they solved this problem? 4A.9 A piece of copper of mass 20.0 g at 100.0 8C is placed in a vessel of negligible heat capacity but containing 50.7 g of water at 22.0 8C. Calculate the final temperature of the water. Assume that no energy is lost to the sur...

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Hi! Could someone please explain to me how they solved this problem? 4.5 In 1750, Joseph Black performed an experiment that eventually led to the discovery of enthalpies of fusion. He placed two samples of water, each of mass 150. g, at 0.00 8C (one ice and one liquid) in a room kept at a constant t...

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I'm having some trouble solving this problem, could someone please walk me through it? 4C.13 An ice cube of mass 50.0 g at 0.0 8C is added to a glass containing 400.0 g of water at 45.0 8C. What is the final tempera- ture of the system (see Tables 4A.2 and 4C.1)? Assume that no heat is lost to the s...

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Hi! I'm having some trouble figuring out this problem. Could someone please walk me through it? 4A.3 Air in a bicycle pump is compressed by pushing in the handle. The inner diameter of the pump is 3.0 cm and the pump is depressed 20. cm with a pressure of 2.00 atm. (a) How much work is done in the c...

Talia Dini - 3I

Since argon gas is an inert gas, adding it will not have an impact on the reaction!

Talia Dini - 3I

An inert gas will not change the equilibrium partial pressures because they are not reactive and will not have an effect on the volume. Hope this helps!

Talia Dini - 3I

Yes, aqueous solutions would be included when calculating the equilibrium constant K. Only solids and liquids would not be included.

Talia Dini - 3I

The equilibrium constant, K, would be affected by a change in temperature. If there is an endothermic reaction and temperature is increased, there will be a shift towards the products and K will increase. However, if there is an exothermic reaction and temperature is increased, there will be a shift...

Talia Dini - 3I

I believe that x would be negligible if it is less than 10^-4, however, just to be sure you can calculate the percent ionization. If the percent ionization is less than 5%, it would be fine to make the assumption that x is negligible.

Talia Dini - 3I

Hi! HClO3 would be a strong acid and ClO3- would be a weak conjugate base.

Talia Dini - 3I

Kc is a type of K. When using Kc, you are calculating the equilibrium constant by using equilibrium concentrations!

Talia Dini - 3I

Hi! The way I distinguish between endothermic and exothermic reactions is that if bonds are being formed, the reaction will be exothermic because energy is being released. However, if bonds are being broken, the reaction will be endothermic because energy is required.

Talia Dini - 3I

Hi! The formula for pka is pka = -log(ka) and the formula for ka is ka = 10^-pka. The larger the pka value, the smaller the ka value and vice versa. Hope this helps!

Talia Dini - 3I

Yes, I believe that your formula for percent ionization is correct!

Talia Dini - 3I

Hi! I would recommend doing the textbook problems that have been assigned, reviewing the sapling homework, doing the UA worksheets, and making sure you know all of the concepts listed on the outlines!

Talia Dini - 3I

Could someone please explain how they went about solving this problem? I'd really appreciate it! 6.19 Hemoglobin (Hb) molecules in blood carry O2 molecules from the lungs, where the concentration of oxygen is high, to the tissues where it is low (see the Interlude following Focus 5). In the tissues ...

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I'm having some problem figuring out this problem, could someone please explain how they solved it?

6D.13 Rank the following solutions in order of increasing pH: (a) 1.0 3 1025 m HCl(aq); (b) 0.20 m CH3NH3Cl(aq); (c) 0.20 m CH3COOH(aq); (d) 0.20 m C6H5NH2(aq). Justify your ranking.

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Hi! Could someone please walk me through how they solved this problem?

6D.9 The percentage deprotonation of benzoic acid in a 0.110 m solution is 2.4%. What is the pH of the solution and the Ka of benzoic acid?

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I'm having some trouble figuring out this problem, could someone please explain it to me? 6C.13 Arrange the following bases in order of increasing strength on the basis of the pKa values of their conjugate acids, which are given in parentheses: (a) ammonia (9.26); (b) methylamine (10.56); (c) ethyla...

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Hi! Could someone please walk me through how I am supposed to solve this problem? 6B.11 A student added solid Na2O to a volumetric flask of volume 200.0 mL, which was then filled with water, resulting in 200.0 mL of NaOH solution. Then 5.00 mL of the solution was transferred to another volumetric fl...

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Hi! I'm a little confused about part f of the question pasted below. On the answer key, it says that the equilibrium composition won't change because changing the amount of water will not affect the reaction. However, on #15 of the Chemical Equilibrium Part 4 Post-Module Assessment, when water (l) i...

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I'm not quite sure how to solve part b of this question, could someone please explain it to me? 5.57 The two air pollutants SO3 and NO can react as follows: SO3(g) 1 NO(g) S SO2(g) 1 NO2(g). (a) Predict the effect of the following changes to the amount of NO2 when the reaction has come to equilibriu...

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I'm having some trouble figuring out this problem. I'd really appreciate it if someone could walk me through it! 5.35 The following plot shows how the partial pressures of reactants and products vary with time for the decomposition of compound A into compounds B and C. All three compounds are gases....

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Hi! I had some trouble figuring out the problem pasted below. Could someone please walk me through it? 5I.19 A reaction mixture that consisted of 0.400 mol H2 and 1.60 mol I2 was introduced into a flask of volume 3.00 L and heated. At equilibrium, 60.0% of the hydrogen gas had reacted. What is the e...

Talia Dini - 3I

Hi! I believe that you should be fine as long as all the numbers in the ICE table have the same units. However, I believe that it is more convenient if all the units are in mol/L so that you do not have to worry about units later on.

Talia Dini - 3I

We neglect the water concentration in the Kw equation because water is in tremendous excess. The concentration of water changes very very slightly so the change is negligible and not included in the Kw equation. Hope this helps!

Talia Dini - 3I

Hi! In order for x to be negligible, K needs to be smaller than 10^-4. One way you can verify your approximation is through the 5% rule which states that if x is less than 5% of the initial value, then x is a valid value.

Talia Dini - 3I

Changes in reactants would be negative whereas changes in products would be positive. Hope this helps!

Talia Dini - 3I

Hi! I believe that you would use Kelvin as the unit for temperature.

Talia Dini - 3I

29. A researcher fills a 1.00 L reaction vessel with 1.84 x 10-4 mol of BrCl gas and heats it to 500 K. At equilibrium, only 18.3 % of the BrCl gas remains. Calculate the equilibrium constant, assuming the following reaction is taking place. 2BrCl(g) ⇌ Br2 (g) + Cl2(g) A. 19.5 B. 8.39 x 10-5 C. 4.98...

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17. Determine the shift in equilibrium, if any, which will occur for the following reactions when the temperature is increased a) Photosynthesis: 6 CO2 (g) + 6 H2O (l) ⇌ C6H12O6(s) + 6 O2 (g) delta H° = +2802 kJ.mol-1 b) The hydrolysis of ATP: ATP (aq) + H2O (l) ⇌ ADP + PO42-(aq) delta H° = -30 kJ.m...

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16. Predict the shift in equilibrium position, if any, which will occur when the temperature is increased. The hydrolysis of ATP: ATP (aq) + H2O (l) ⇌ ADP + PO42-(aq) delta H° = -30 kJ.mol-1 A. Not enough information B. No change C. Shifts to left D. Shifts to right Hi! Could someone please walk me ...

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15. The photosynthesis reaction, 6 CO2(g) + 6 H2O(l) ⇌ C6H12O6(aq) + 6 O2(g), is endothermic. What effect will the following changes have on the equilibrium composition. a) Water is added. b) The partial pressure of CO2 is decreased. A. a) Decrease [C6H12O6] and [O2], b) Decrease [O2] B. a) Decrease...

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13. State whether the equilibrium shifts towards products, reactants, or neither when the given change occurs. 2 HI(g) + Cl2(g) ⇌ 2 HCl(g) + I2(s) delta H° = -238.0 kJ.mol-1 i. The volume of the system is compressed. ii. The temperature of the system is decreased. A. i = Products, ii = Products B. i...

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Hi! HF is a weak acid because the bond length between H and F is short. Thus, when placed in a solution, it will be hard for the bond to break and for the ions to easily dissociate.

Talia Dini - 3I

If you have a pH of 8.85, the pOH would equal 5.15 (14 - 8.85). The H+ concentration would equal 10^(-8.85). The OH- concentration would equal 10^(-5.15)

Talia Dini - 3I

A bronsted acid is a proton donor. A bronsted base is a proton acceptor. A lewis acid is a lone pair acceptor. A lewis base is a lone pair donor.

Talia Dini - 3I

Hi, the wedge means towards you while the dash means away from you. Hope this helps!

Talia Dini - 3I

No, seesaw and trigonal pyramidal are not the same shape. Seesaw has 4 bonding pairs and 1 lone pair while trigonal pyramidal has 3 bonding pairs and 1 lone pair.

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The bond angles should be less than 90 degrees

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Hi! Bent and angular describe the same shape

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I'm having trouble figuring out this problem, could someone please explain I would complete it?

9C.7 Which of the following isomers of diaminobenzene can form chelating complexes? Explain your reasoning.

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Hi! Could someone please explain to me how I would complete this problem? 9C.5 Which of the following ligands can be polydentate? If the ligand can be polydentate, give the maximum number of places on the ligand that can bind simultaneously to a single metal center: (a) HN(CH2CH2NH2)2; (b) CO322; (c...

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I am confused why the answer for part a is hexacyanoferrate(II) and not hexacyanidoferrate(II). Could someone please explain this to me? 9C.1 Name each of the following complex ions and identify the oxidation number of the metal: (a) [Fe(CN)6]42; (b) [Co(NH3)6]31; (c) [Co(CN)5(OH2)]22; (d) [Co(NH3)5...

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Could someone please explain how I would complete this problem? 2.45 Consider the bonding in H2CPCHCHO. (a) Draw the most important Lewis structure. Include all nonzero formal charges. (b) Identify the composition of the bonds and the hybridization of each lone pair—for example, by writing s(H1s,C2s...

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Would both a compound with 2 bonding pairs and 1 lone pair and a compound with 2 bonding pairs and 2 lone pairs be considered angular?

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Hi! I'm having trouble with this problem, could someone please explain how I would complete it? 2F.15 Noting that the bond angle of an sp3 hybridized atom is 109.5 and that of an sp2 hybridized atom is 120, do you expect the bond angle between two hybrid orbitals to increase or decrease as the s-cha...

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Why is CH2Cl2 polar but C6H4Cl2 is nonpolar?

Talia Dini - 3I

Hi! Yes, a single bond would consist of one sigma bond. To add on, a double bond would consist of one sigma bond and one pi bond. A triple bond would consist of one sigma bond and two pi bonds.

Talia Dini - 3I

Yes! Bonding pairs and lone pairs are considered regions of electron density! Hope this helps!!

Talia Dini - 3I

Hi! I believe that we will have to memorize the shapes and bond angles for the final!

Talia Dini - 3I

Hi! Delocalized pi bonds would exist in resonance structures. Hope this helps!

Talia Dini - 3I

PO4^3- has four hybrid orbitals and not five because the double bond on the phosphorus atom only counts as one region of electron density.

Talia Dini - 3I

Hi! The hybridization of the carbon and oxygen atoms depends on how many regions of electron density it has. The carbon atom has 4 regions of electron density because it has 4 single bonds. The oxygen atom has 4 regions of electron density because it has 2 single bonds and 2 lone pairs. Thus, the hy...

Talia Dini - 3I

We can determine the number of sigma and pi bonds a molecule has by looking at how many single, double, and triple bonds are in the molecule. A single bond would have 1 sigma bond. A double bond would have 1 sigma bond and 1 pi bond. A triple bond would have 1 sigma bond and 2 pi bonds.

Talia Dini - 3I

Hi! Yes, as Dr. Lavelle mentioned in one of his lectures, H can never be a central atom when drawing a lewis structure.

Talia Dini - 3I

Hi! I had some trouble drawing the lewis structure of N5+. This is asked of me in exercise 7 in focus 2. Can someone please explain to me how they attempted to do it?

Talia Dini - 3I

Hi! Yes, you are correct. Electronegativity increases across a period and decreases down a group. It follows the same trend as electron affinity and ionization energy!

Talia Dini - 3I

Yes, there is repulsion between lone pair electrons. There is also repulsion between bonding pair electrons. The strength of these repulsions are different and are as follows: the lone pair-lone pair repulsion is stronger than the lone pair-bonding pair repulsion which is stronger than the bonding p...

Talia Dini - 3I

Yes! Expanded octets can be expanded even further past 10 valence electrons.

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