Question 1

A chemical reaction releases 55.2 kcal. How many kilojoules does this correspond to? (Use $$1 	ext{ cal} = 4.184 	ext{ J}$$ and $$1 	ext{ kcal} = 1000 	ext{ cal})$$

Accepted Answer

$$231 	ext{ kJ}$$

Question 2

One serving of fudge brownie contains $$7.00 	ext{ g} of $$fat, $$2.00 	ext{ g} of $$protein, and $$22.0 	ext{ g} of $$carbohydrate. If fat provides $$9 	ext{ Cal/g}$$, protein $$4 	ext{ Cal/g}$$, and carbohydrate $$4 	ext{ Cal/g}$$, how many Calories does 2 servings provide?

Accepted Answer

$$294 	ext{ Cal}$$

Question 3

Which bond is the strongest among the following hydrogen-halogen bonds?

Accepted Answer

H–F

Question 4

Consider the reaction: $$\mathrm{C_3H_8(g) + 5\ O_2$(g) ightarrow 3\ CO_2$(g) + 4\ H_2O(g)}$$, where $$\Delta H = -531 	ext{ kcal}. $$Which statement is true?

Accepted Answer

The bonds formed in the products are stronger than the bonds broken in the reactants.

Question 5

Catalysts accelerate a reaction by ________.

Accepted Answer

lowering the energy of activation

Question 6

Which $$K$$ value below is consistent with an equilibrium system in which the products are largely favored?

Accepted Answer

$$K = 5.2 	imes 10^4$

Question 7

When the pressure of a gas phase reaction at equilibrium decreases, in which direction does the equilibrium shift?

Accepted Answer

The equilibrium shifts in the direction that increases the number of moles of gas.

Question 8

Consider the reaction: $$\mathrm{N_2$(g) + O_2$(g) ightarrow 2\ NO(g)}. If$$ $$[\mathrm{N_2$}] = 0.520 	ext{ M}$$, $$[\mathrm{O_2$}] = 0.0662 	ext{ M}$$, and $$[\mathrm{NO}] = 0.00956 	ext{ M} at $$equilibrium, what is the value of $$K$$?

Accepted Answer

$$K = 0.00265$$

Question 9

Which of the following will increase the rate of a reaction?

Accepted Answer

All of these changes will increase the rate of a reaction.

Question 10

A patient's systolic pressure is measured as $$128 	ext{ mm Hg}. $$What is this pressure in atm? (Use $$1 	ext{ atm} = 760 	ext{ mm Hg})$$

Accepted Answer

$$0.168 	ext{ atm}$$

Question 11

A sample of neon gas has a volume of $$5.0 	ext{ mL} at a $$pressure of $$1.50 	ext{ atm}. $$What is the pressure exerted by the gas if the volume is increased to $$30.0 	ext{ mL}$$, at constant temperature? (Use $$P_1V_1 = P_2V_2)$$

Accepted Answer

$$0.25 	ext{ atm}$$

Question 12

A $$54.2 	ext{ L}$$ sample of gas at $$115 	ext{ K} is $$heated to $$345 	ext{ K}$$, at constant pressure. What volume does the gas now occupy? (Use $$\frac{V_1$}{T_1$} = \frac{V_2$}{T_2$})$$

Accepted Answer

$$163 	ext{ L}$$

Question 13

The temperature of a $$0.750-L $$gas sample at $$25 ^\circ 	ext{C}$$ and $$2.00 	ext{ atm} is $$changed to $$250 ^\circ 	ext{C}. $$What is the final pressure of the system, at constant volume? (Use $$\frac{P_1$}{T_1$} = \frac{P_2$}{T_2$}$$, with temperatures in Kelvin)

Accepted Answer

$$3.51 	ext{ atm}$$

Question 14

A weather balloon contains $$233 	ext{ L} of $$helium at $$22 ^\circ 	ext{C}$$ and $$760 	ext{ mm Hg}. $$What is the volume of the balloon when it ascends to an altitude where the temperature is $$-54 ^\circ 	ext{C}$$ and $$511 	ext{ mm Hg}$$? (Use $$\frac{P_1V_1}{T_1$} = \frac{P_2V_2}{T_2$})$$

Accepted Answer

$$116 	ext{ L}$$

Question 15

Which cylinder at STP will contain the greatest number of gas particles?

Accepted Answer

All of the cylinders contain the same number of gas particles.

Question 16

A sample of gas contains four gases with the following partial pressures: He ($$113 	ext{ mm Hg}$$), Ne ($$184 	ext{ mm Hg}$$), Ar ($$35 	ext{ mm Hg}$$), and Xe ($$445 	ext{ mm Hg}). $$What is the total pressure of the sample? (Use $$P_{	ext{total}} = P_{	ext{He}} + P_{	ext{Ne}} + P_{	ext{Ar}} + P_{	ext{Xe}})$$

Accepted Answer

$$777 	ext{ mm Hg}$$

Question 17

Which is an ionic solid?

Accepted Answer

KCl

Question 18

Hydrogen bonding occurs with molecules that contain O-H and N-H bonds as well as molecules with which other type of bond?

Accepted Answer

F-H

Question 19

What is the correct equilibrium constant expression for the reaction $$2\ \mathrm{C_2H_6(g)} + 7\ \mathrm{O_2$(g)} \rightarrow 4\ \mathrm{CO_2$(g)} + 6\ \mathrm{H_2O(g)}$$?

Accepted Answer

$$K = \frac{[\mathrm{CO_2$}]^4[\mathrm{H_2O}]^6}{[\mathrm{C_2H_6}]^2[\mathrm{O_2$}]^7}$$

Question 20

Refer to the diagram showing two closed containers, Liquid A and Liquid B. Which liquid exhibits the stronger intermolecular forces?

Accepted Answer

Liquid A

Chem 140A Exam 3 Study Guidance

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