CHEMISTRY COMMUNITY

Juliana Chopelas 1A

Rate constants are always positive due to the Arrhenius equation but the slope is negative because it shows how the reactants are affected in the first order reaction.

Juliana Chopelas 1A

O2 by itself has an oxidation number of zero but if O was in a compound it would have an oxidation number of -2

Juliana Chopelas 1A

Firs you want to determine which elements are reducing and oxidizing. Once you do this, you write the half reactions for both the oxidation element and reducing element. From here you make sure the number of electrons can cancel out. So if on reaction only has 1 electron but the other has 2, you wan...

Juliana Chopelas 1A

Elementary reactions show the progress of a reaction so it is broken down into many steps to show this. For an elementary reaction the reaction rate is directly proportional to the concentration fo the reactant.

Juliana Chopelas 1A

the units for rate constant will change depending on the order of the reaction but the units for rate is the same

Juliana Chopelas 1A

Zero order reaction: graph is concentration A v time, with a straight line where k is -slope
First order reaction: graph is ln of concentration A v time, with a straight line where k is -slope
Second Order reaction: graph is 1/concentration A v time, with a straight line where k is +slope

Juliana Chopelas 1A

K is the normal rate of a reaction while k prime is the reverse rate of a reaction

Juliana Chopelas 1A

I am not sure if there is a time where catalysts are not saturated or the range of concentrations of the reactants for this but I do know that a zero order reaction is the only reaction whose rate is influenced by the how saturated a catalyst is.

Juliana Chopelas 1A

Negative in a rate law is used to show when reactants are being all used up

Juliana Chopelas 1A

A zero order reaction is one whose rate does not depend on the concentration of reactants so if the concentrations increase or decrease, the rate does not change. A first order reaction is one whose rate is directly proportional to the concentration of the reactants. A second order reactions rate de...

Juliana Chopelas 1A

You can look at the reactions graph. Which ever graph produces a straight line will give you the reaction order. For zero order the graph would be (A) v time and would give a straight line with a -slope. First order reaction would be ln(A) v time and would give a straight line with a -slope. Second ...

Juliana Chopelas 1A

Second order reactions have a graph of 1/(A) v time. If the reaction is second order, the graph would appear linear with k being +slope of the line.

Juliana Chopelas 1A

Reaction order is dependent upon the concentrations of the reactions v time. If you are given a set of data, you can solve for n and m (the exponents for each reactant) by comparing two different trials that have the same concentrations for one reactant and different concentrations for the other to ...

Juliana Chopelas 1A

If the reaction is first order then the graph would be linear with a slope of -K. The same goes for zero and second order reactions. Their graphs should be linear.

Juliana Chopelas 1A

Reaction orders will always be a whole number so if you ever get a decimal you either round up or round down. If the decimal is 1.999 then the reaction order will be 2. If the decimal is 1.0001 then the reaction order with be 1.

Juliana Chopelas 1A

Current is the flow of electrons through a circuit while voltage is the force that pushes or drives these electrons through the circuit. So the relationship is how hard the force is will determine how many electrons get pushed through the circuit. So if something has a high voltage this means there ...

Juliana Chopelas 1A

Yes the sign would be flipped as you would hav veto flip the oxidation reaction therefore you flip the sign for the value of E.

Juliana Chopelas 1A

When you get the half reactions, one has 12e while the other has 2e so you must multiply the equation with 2e by 3 so the e's cancel out. This is how you get 3 as the coefficient for the molecules that have carbon. You go from 14H to 8H because the H's are on opposite sides in the half reactions tha...

Juliana Chopelas 1A

When you are trying to sum up both half reactions, you can do some simplifying by getting rid of the 12OH in the second half reaction and subtracting 12 from the 24OH on the first half reaction (you can do this because they are on opposite sides of each other) which leaves you with 12OH on the react...

Juliana Chopelas 1A

Platinum is an inert conductor that is often used as an electrode to transfer electrons through the galvanic cell. If platinum was not there, there would be no metal to transfer these electrons from anode to cathode. Platinum does not react easy so it is not involved in the redox reaction when used.

Juliana Chopelas 1A

Delta S is equal to entropy so on a question when asked to calculate entropy you will use a delta s equation. Just normal delta s is the change in entropy, delta s surroundings is the change of entropy in the surroundings, and delta s total is the change of entropy of the surroundings and change of ...

Juliana Chopelas 1A

When a phase change is happening you will use q=mdeltah or q=ndeltah depending on whether you are given mass or moles. When the substance is heating up or the diagonal line on the curve, you will used q=mcdeltaT or q=ncdeltaT once again depending on whether you are given moles or mass.

Juliana Chopelas 1A

You can use density to find "n" or even replace "n" in PV=nRT since density is mass/volume

Juliana Chopelas 1A

The fractions just represent the molar heat capacity for constant pressure and constant volume when plugging it into an equation. Also I think the question would specify "at constant volume" or "at constant pressure" to know when to use it.

Juliana Chopelas 1A

at constant temperature and pressure, delta h is going to be what q is so if q is positive then so is delta h and same for if q were to be negative

Juliana Chopelas 1A

When you are compressing something, the volume is decreasing therefore there will be a change in concentration so it will shift to the side with less of moles of gas because the concentration is decreasing.

Juliana Chopelas 1A

q=mCAT is for when you are given mass and q=nCAT is when you are given moles. Both are the same equation and determine the heat energy of a substance on a heating curve.

Juliana Chopelas 1A

It is not necessarily obvious without looking in tables for energies and enthalpies. You can try to guess by looking to see if bonds are broken and formed but you won't truly know until you calculate to see if a reaction is exothermic or endothermic.

Juliana Chopelas 1A

Work is not a state function because it is relative to how far or the distance an object has moved. Work depends on the path it takes to get there. Since work is not a state function heat cannot be either because the change of internal energy is dependent upon the sum of heat and work transferred be...

Juliana Chopelas 1A

Work is always equal to the change in internal energy and internal energy = ( heat supplied to system) - (work done by a system).

Juliana Chopelas 1A

The q of the system is equal to the q of the surroundings meaning any energy gained or lost by the system is equal to any energy gained or lost by the surroundings. They also have opposite signs as if heat is lost by the system, it is gained by the surroundings and vice versa

Juliana Chopelas 1A

Since you are heating up the copper kettle, you are thus heating up the water so you must add the two together to get the heat change for the two

Juliana Chopelas 1A

a calorimeter is a normal insulated container while a bomb calorimeter consists of a sealed metal container that is in another sealed container immersed in water to measure the heat combustion of a reaction

Juliana Chopelas 1A

delta u is only equal to delta h when pressure is constant and volume doesn't change

Juliana Chopelas 1A

Moles and liters count for the sig figs that is why there are 3 of them

Juliana Chopelas 1A

heat is energy transferred between systems and its surroundings and the amount of heat transferred between the system and surroundings does depend on the path it takes to heat something up while for temperature it doesn't matter how a system goes from one temp to the other, only the initial and fina...

Juliana Chopelas 1A

extensive and intensive functions depend on how the property changes when the size of a system changes while state functions only depend on initial and final values of a system

Juliana Chopelas 1A

Enthalpy is a state function because it only depends on the initial and final states of something and not the whole path to get there.

Juliana Chopelas 1A

If you look at a heating curve for water, and you look at liquid at 100 degrees the water will drop from 100 to about 25 degrees when it touches the skin as about 5 kj of energy is released. When steam touches the skin, it is suddenly going form a gas to a liquid so much more energy or heat is being...

Juliana Chopelas 1A

Adding an inert gas does not change the concentrations of any of the reactants or products in a system therefore the reaction is not unbalanced so to speak. When changing the volume, the pressure changes which changes the concentration of the reactants or products therefore the reaction will shift t...

Juliana Chopelas 1A

When a reactant is reduced, the equilibrium will shift towards the products in order to make more reactants to balance out the system

Juliana Chopelas 1A

I wouldn't stress too much about this on the test but we will probably have to know it at some point

Juliana Chopelas 1A

The threshold is less than 10^-3 and then you would calulate percent ionization which is (H3O+ ions dissociated at equilibrium)/(initial acid) and multiply that by 100. This percent value must be under 5% to be an accurate approximation

Juliana Chopelas 1A

A buffer solution that resist changes in pH or prevents the fluctuation in pH. So if you want to achieve this, a buffer can only be used with a weak base and its conjugate acid or a weak acid and its conjugate base. You cannot create a buffer with a strong acid or strong base so look for the weak on...

Juliana Chopelas 1A

In the equilibrium expression, reactants are int he denominator so if the reactants are favored there are way more of them being produced because reactants want to stay as reactants, similarly, if the K was greater than 10^-3 the products would be favored, producing more products as products want to...

Juliana Chopelas 1A

Exothermic reaction will always have a decrease in temperature as energy is being released. Once the temperature rises it will switch to endothermic as energy is being absorbed.

Juliana Chopelas 1A

D is an open system because it has interactions externally with the environment, it is releasing energy into the air. C is a closed system because the bomb calorimeter is designed to keep gases in so no gas is released to interact with the environment.

Juliana Chopelas 1A

In some equations H2O is a gas so when writing the expression for K, would H2O be included if it was a gas?

Juliana Chopelas 1A

Hi! So the complete ionic equation basically breaks down all aqueous species in the equation. So the complete net ionic equation would look like this... 2Ag(aq) + NO3(aq) +2Na(aq) + OH --> Ag2O(s) + 2Na + NO3(aq) +H2O(l) For the net ionic equation you "cancel out" what is the same on both ...

Juliana Chopelas 1A

Does the reaction quotient "Q" have a specific unit if one is not listed or mentioned in a problem?

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