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When does a gas behave most like an ideal gas?

At low temperatures, low volume, low intermolecular interactions

At high temperatures, high volume, low intermolecular interactions

At low volumes, high temperatures, and high intermolecular interactions

At high temperature, high volumes, and high intermolecular interactions

At low temperatures, high volume, and low intermolecular interactions

Explanation

The ideal gas law assumes the gas particles are non-interacting and small relative to the size of their container. At high temperatures the gas molecules are moving fast enough to shorten the time scale for any interactions. At high volumes, the molecular size becomes small relative to the size of the container, and the low interactions mean the molecules act more independently.

The rate law of the reaction, $A + B \rightarrow C$ , is $\textup{Rate} = k\left [ A\right ]^{3}$ . Which of the following does not increase the rate of the reaction?

Increasing the concentration of

Adding the catalyst to the reaction

Increasing the temperature of the reaction

Increasing the concentration of

Explanation

The reactant is not included in the rate law expression, and therefore altering its concentration does not affect the rate of the reaction. Catalysts always increase the rate of reactions by lowering its activation energy. Increasing temperature (average kinetic energy of the molecules) increases the frequency of collisions, and increases the proportion of collisions that have enough energy to overcome the activation energy and undergo a chemical reaction. Increasing the concentration of will increase the rate of the reaction as indicated by the rate law.

What volume of 0.5M NaOH is necessary to neutralize 15mL of 1.0M nitrous acid?

30mL

10mL

30L

Explanation

Both the acid and the base provide one equivalent of the necessary ions (H+ and OH–, respectively) and therefore you can use the equation M1V1 = M2V2.

(1)(15) = (0.5)V2

V2 = 30mL

What volume of 0.5M NaOH is necessary to neutralize 15mL of 1.0M nitrous acid?

30mL

10mL

30L

Explanation

Both the acid and the base provide one equivalent of the necessary ions (H+ and OH–, respectively) and therefore you can use the equation M1V1 = M2V2.

(1)(15) = (0.5)V2

V2 = 30mL

Which of the following compounds contains the most π bonds?

CO2

H2O

CH4

NH3

C2H6

Explanation

π bonds occur when there is greater than a single bond (double or triple bond). The only compound listed with double bonds or greater is CO2, meaning it is the one that contains the most π bonds.

A chemistry student is trying to calculate how long it will take a power source of to heat a sample of ice from $-35^{o}C$ to $75^{o}C$ . Given that the specific heat capacity of ice is $2.06\frac{J}{g^{o}C}$ , the specific heat capacity of liquid water is $4.184\frac{J}{g^{o}C}$ , and the heat of fusion for water is $334.16\frac{J}{g}$ , how long will this process take?

There is not enough information to determine the amount of time needed for the process described

Explanation

In order to solve this problem, we'll need to break it up into steps.

Step 1: Calculate the amount of energy necessary to raise the sample of ice from $-35^{o}C$ to $0^{o}C$ . To do this, we'll need to use the following equation:

$q_{1}=mc_{H_{2}O(s)}\Delta T$

$q_{1}=( 20\cdot 10^{3}g)\left ( 2.06\frac{J}{g^{0}C} \right )\left ( 35^{o}C \right )=1.44\cdot 10^{6}J$

Step 2: Calculate the amount of energy necessary to convert the sample at $0^{o}C$ from ice to water. We'll need to make use of the following equation:

$q_{2}=m\Delta H_{fus(H_{2}O)}$

$q_{2}=\left ( 20\cdot 10^{3}g \right )\left ( 334.16\frac{J}{g} \right )=6.68\cdot 10^{6}J$

Step 3: Calculate the amount of energy necessary to convert the sample of water from $0^{o}C$ to $75^{o}C$ .

$q_{3}=mc_{H_{2}O(l)}\Delta T$

$q_{3}=\left ( 20\cdot 10^{3}g \right )\left ( 4.184\frac{J}{g^{o}C} \right )\left ( 75^{o}C \right )=6.28\cdot 10^{6}J$

Step 4: Sum the amount of energy from the previous 3 steps. This value is the total amount of energy for the entire process.

$q_{Total}=q_{1}+q_{2}+q_{3}=1.44\cdot 10^{7}J$

Step 5: Now that we know the total amount of energy needed for the process, we need to calculate the time based on the amount of power provided.

$P=\frac{q_{Total}}{t}$

$t=\frac{q_{Total}}{P}=\frac{\left ( 1.44\cdot 10^{7}J \right )}{(100\frac{J}{s}) }=1.44\cdot 10^{5}s$

$t=(1.44\cdot10^{5}s)\left ( \frac{1hr}{3600s} \right )=40hrs$

$Fe_{(s)} + 2HCl_{(aq)} \rightarrow FeCl_{2(aq)} + H_{2(g)}$

For the redox reaction shown, which of the following half reactions occurs in the anode?

$Fe \rightarrow Fe^{2+} + 2e^{-}$

$Fe \rightarrow Fe^{3+} + 3e^{-}$

$Fe^{2+} + 2e^{-} \rightarrow Fe$

$2H_{2} + 2e^{-} \rightarrow H_{2}$

Explanation

Recall that oxidation always occurs at the anode (in both the electrochemical and galvanic cells). loses two electrons in this case to become $Fe^{2+}$ . The presence of $Fe^{2+}$ is hinted by the ionic compound .

$O_{_{3}} \rightarrow O_{_{2}} + O$ (slow)

$O + O_{_{3}} \rightarrow 2O_{_{2}}$ (fast)

The mechanism for decomposition of ozone is shown. What is the intermediate of the process?

$O_{2}$

$2O_{2}$

$O_{3}$

Explanation

Intermediate is created and destroyed, and therefore does not appear on the net equation, which is $2O_{3} \rightarrow 3O_{2}$ . Thus, the intermediate is . Note that when asked for an intermediate, the coefficient in front of it is not used, rather we are looking for the species that is a product of one reaction and a reactant in a subsequent step.

Chaning which of the following factors can alter the rate of a zero-order reaction?

Temperature

Increasing the concentration of reactants

Increasing the concentration of products

Decreasing the concentration of products

Explanation

A zero-order reaction has a rate of formation of product that is independent of changes in concentrations of any of the reactants; however, since the rate constant itself is dependent on temperture, changing the temperature can alter the rate.

How many electrons are involved in the following reaction?

$MnO_4^-+ I^-\rightarrow I_2+Mn^{2+}$