Chemistry: Chapter 6

Which of the following energy quantities is equivalent to 578 J?

0.138 kcal

Consider the combustion reaction of propane: C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g), where ΔH = -531 kcal. If 6.70 × 10^4 kcal of energy is released in the reaction, how many grams of oxygen were consumed?

2.02 × 10^4 g of O2

Consider the combustion reaction of propane: C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g), where ΔH = -531 kcal. If 1.24 × 10^5 kcal of energy is released in the reaction, how many moles of propane were burned?

234 mol of C3H8

Consider the reaction, C2H4(g) + H2(g) → C2H6(g), where ΔH = -137 kJ. How many kilojoules are released when 55.3 g of C2H4 reacts?

270. kJ are released

Which of the following energy quantities is equivalent to 11.9 kcal?

49.8 kJ

What is the gas phase chemical reaction that corresponds to the equilibrium constant expression shown below? K= [C]^2/ ([A]^4[B]^2)

4A+2B---> 2C <---

A chemical reaction requires 31.39 kJ. How many kilocalories does this correspond to?

7.502 kcal

Consider the reaction, 3 NO2(g) + H2O(l) → 2 HNO3(aq) + NO(g), where ΔH = -137 kJ. How many kilojoules are released when 92.3 g of NO2 reacts?

91.6 kJ are released

Which of the following is ALWAYS necessary for a chemical reaction to occur between two reactants, A and B?

A and B must collide with the proper orientation and with a certain minimum amount of energy

Which of the following is a true statement about the energy diagram shown below?

A labels the Ea of the reaction and B labels ΔH of the reaction.

Which value (if any) in each pair corresponds to a faster reaction?

Ea = 1 kcal

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

K = 3.7 x 10^-8

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

K = 5.2 x 10^4

Consider the reaction: C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g), where ΔH = -531 kcal. Which statement concerning this reaction is true?

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

The rusting of iron is described by the reaction: 4 Fe(s) + 3 O2(g) → 2 Fe2O3(s). The formation of rust on an exposed piece of iron typically takes several months. Which of the following is NOT a reasonable assumption about this chemical reaction?

The formation of rust has a low activation energy.

The rate of a chemical reaction increases with an increase in the concentration of one or more reactants. This is best explained by which statement?

The higher concentration of reactants increases the frequency of collisions between molecules.

The reversible reaction: PCl3(g) + Cl2(g) PCl5(g), has K = 0.5. Based on the molecular art shown below, what can be inferred about the reaction conditions?

The reaction has not yet reached equilibrium.

One step in the metabolism of glucose is depicted below. Which statement best describes how the equilibrium system would respond if the amount of dihydroxyacetone phosphate is decreased?

The system would shift to the right, producing more dihydroxyacetone phosphate and glyceraldehyde 3-phosphate.

A reversible reaction in which K = 9.65 × 10^-14 contains a negligible amount of reactants at equilibrium.

false

Consider the reaction: 2 C2H6(g) + 7 O2(g) → 4 CO2(g) + 6 H2O(g). Increasing the concentration of C2H6(g) will decrease the activation energy.

false

In the energy diagram shown below, the ΔH of the reaction is labeled by D.

false

Increasing the temperature of a reaction mixture usually results in a decrease in the reaction rate.

false

Once equilibrium is reached in a chemical reaction, reactants stop forming products.

false

The equilibrium constant expression for the reversible reaction: CHCl3(g) + 3 HCl(g)<-> CH4(g) + 3 Cl2(g) is K= ([CH4][Cl2]^3)/([CHCl3]^3[HCl])

false

The expression for the equilibrium constant, K, for the general reaction: a A + b B c C + d D is K=([C][D])/([A][B])

false

The larger the K for a reaction, the faster the reaction.

false

When the equilibrium constant for a reaction is much less than one (K < 1), the concentration of the products is larger than the concentration of the reactants.

false

In the reaction: 2 C2H6(g) + 7 O2(g) → 4 CO2(g) + 6 H2O(g), increasing the concentration of C2H6(g) will ________.

increase the reaction rate

For an endothermic reaction at equilibrium, increasing the temperature ________.

increases the rate of the forward reaction to form more products

Catalysts accelerate a reaction by ________.

lowering the energy of activation

When reactants can come together and form products, and products can come together to re-form reactants, the reaction is called a ________ reaction.

reversible

A catalytic converter uses a catalyst to catalyze three reactions that clean up the exhaust from an auto engine. Which element is not used as a catalyst in catalytic converters?

sulfur

A reversible reaction has reached equilibrium when which condition is established?

the forward and reverse reaction rates become equal

An equilibrium constant with a value of 8.0 × 10^6 indicates that at equilibrium ________.

the products are favored

Activation energy is the minimum amount of energy necessary for a reaction to occur.

true

Ammonia (NH3) is synthesized by the reaction of nitrogen and hydrogen in the presence of an iron catalyst according to the equation below. Removing the iron catalyst would decrease the reaction rate. Fe 3H2 (g) + N2 (g) ----> 2NH3 (g)

true

Bond dissociation energies are always positive numbers.

true

Breaking a chemical bond requires energy.

true

Consider the following reversible reaction at equilibrium: 2 NO(g) + O2(g) <--> 2 NO2(g). If the pressure inside the reaction vessel is increased, the equilibrium will shift to the right.

true

Consider the following reversible reaction at equilibrium: CO(g) + Cl2(g) <--> COCl2(g). If chlorine gas is added to the reaction vessel, the equilibrium will shift to the right.

true

Consider the following reversible reaction at equilibrium: CO(g) + Cl2(g)<--->COCl2(g). If chlorine gas is added to the reaction vessel, the concentration of carbon monoxide will decrease.

true

Consider the reaction: 2 C2H6(g) + 7 O2(g) → 4 CO2(g) + 6 H2O(g). Decreasing the concentration of C2H6(g) will decrease the reaction rate.

true

Energy is the capacity to do work.

true

Enzymes are proteins that act as biological catalysts.

true

Exothermic reactions involve the formation of products having lower energy than the reactants.

true

In order to cause an endothermic equilibrium reaction to shift in a direction to form more products, the reaction must be heated.

true

Increasing the concentration of the reactants in a chemical reaction increases the number of collisions, and the reaction rate increases.

true

Le Châtelier's principle is a general rule used to explain the effect of a change in reaction conditions on equilibrium.

true

The difference in energy between the reactants and the transition state is called the energy of activation, symbolized by Ea.

true

The stronger the bond, the higher its bond dissociation energy.

true