Q: Which of the following aqueous solutions will have the lowest freezing point? Assume ideal behavior.

$$0.2\ \text{m}\ \text{Na}_2\text{SO}_4$$

Question 1

A solution is prepared by dissolving 10.0 g of NaCl in 100.0 g of water. What is the molality of the solution? (Molar mass of NaCl = 58.44 g/mol)

Accepted Answer

$$1.71\ 	ext{mol/kg}$$

Question 2

Which of the following aqueous solutions will have the lowest freezing point? Assume ideal behavior.

Accepted Answer

$$0.2\ 	ext{m}\ 	ext{Na}_2	ext{SO}_4$$

Question 3

A reaction is first order in A and second order in B. What is the correct rate law for this reaction?

Accepted Answer

$$	ext{rate} = k[A][B]^2$$

Question 4

Which of the following statements best explains why salt is spread on icy roads in winter?

Accepted Answer

Salt lowers the freezing point of water, causing ice to melt at lower temperatures.

Question 5

The rate constant for a reaction is $$2.5 	imes 10$$^{-3}$$\ 	ext{s}^{-1} at$$ $$25^\circ	ext{C}. $$What is the half-life for this first-order reaction?

Accepted Answer

$$277\ 	ext{s}$$

Question 6

A catalyst increases the rate of a chemical reaction by:

Accepted Answer

Lowering the activation energy of the reaction.

Question 7

Which of the following is the correct integrated rate law for a second-order reaction with respect to A?

Accepted Answer

$$\frac{1}{[A]} = kt + \frac{1}{[A]_0}$$

Question 8

A solution contains 0.10 M glucose ($$C_6H_{12}O_6$) and 0.20 M sodium chloride. What is the total osmolarity of the solution?

Accepted Answer

$$0.50\ 	ext{osmolar}$$

Question 9

Which of the following best describes the effect of increasing temperature on the rate constant $$k$$ for most chemical reactions?

Accepted Answer

$$k$$ increases because more molecules have sufficient energy to overcome the activation barrier.

Question 10

A reaction has an activation energy of $$50\ 	ext{kJ/mol}. If $$the temperature is increased from $$300\ 	ext{K} to$$ $$310\ 	ext{K}$$, what happens to the rate constant?

Accepted Answer

The rate constant increases.

Question 11

Which of the following is a correct statement about reaction intermediates?

Accepted Answer

They are formed in one step and consumed in a subsequent step of the reaction mechanism.

Question 12

A reaction is found to be second order overall. If the concentration of the reactant is doubled, what happens to the rate?

Accepted Answer

The rate increases by a factor of 4.

Question 13

Which of the following is the best explanation for why increasing the concentration of reactants generally increases the rate of reaction?

Accepted Answer

There are more frequent collisions between reactant molecules.

Question 14

Which of the following is the correct expression for the osmotic pressure ($$\Pi) of a $$dilute solution?

Accepted Answer

$$\Pi = MRT$$

Question 15

A reaction mechanism consists of the following steps:
Step 1: $$A + B \rightarrow X ($$slow)
Step 2: $$X \rightarrow C ($$fast)
What is the rate law for the overall reaction?

Accepted Answer

$$	ext{rate} = k[A][B]$$

Question 16

Which of the following points on a reaction energy diagram represents the transition state?

Accepted Answer

The highest point along the reaction coordinate.

Question 17

Which of the following is true for an exothermic reaction?

Accepted Answer

The energy of the products is lower than that of the reactants.

Question 18

A solution is made by dissolving 5.00 g of urea ($$	ext{NH}_2	ext{CONH}_2) in 100.0 g of $$water. What is the mole fraction of urea in the solution? (Molar mass of urea = 60.06 g/mol)

Accepted Answer

$$0.0138$$

Question 19

Which of the following best describes the role of an enzyme in a biochemical reaction?

Accepted Answer

It acts as a catalyst, lowering the activation energy.

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