Homework Pack # 5

Homework Pack # 5

Homework Pack # 5

  1. Determine the specific heat of a material if a 35 g sample absorbed 48 J as it was heated from 293 K to 313 K.
  1. If 980 kJ of energy are added to 6.2 L of water at 291 K, what would be the final temperature of the water
  1. Base your answers to the following questions on the diagram below:
  1. Label on this diagram the PE of the reactants, the PE of the products, the activation energy, and the PE of the activated complex.
  2. Is the reaction exothermic or endothermic?
  3. What is ΔH for this reaction?
  1. Base your answers to the following questions on the information below.

Cold packs are often used to prevent swelling of certain athletic injuries. The pack contains ammonium nitrate and water in separate compartments. When the pack is squeezed, the partition breaks mixing the components and forming a solution which turns very cold.

Below is the reaction:

NH4NO3(s)  NH4NO3(l)

  1. Based on the information above, is the reaction endothermic or exothermic?
  1. Based on the information above, is there an increase or decrease in entropy of the system within the cold pack if it is used? Explain your answer.
  1. Is the value of ΔH positive or negative?
  1. A student wishes to determine how the rate of reaction of magnesium strips with hydrochloric acid, HCl (aq), varies as a function of temperature of the HCl (aq). Give two additional factors, other than the temperature, which could affect the rate of reaction and must be held constant during the experiment.
  1. Give a simple reaction mechanism for the following reaction:

Mg + 2HCl  MgCl2 + H2

Base your answers to questions 7 and 8 on the information and diagram below, which represent the changes in potential energy that occur during the given reaction.

  1. Answer the following:
  2. Does the diagram illustrate an exothermic or an endothermic reaction?
  3. State one reason, in terms of energy, to support your answer.
  1. On the diagram provided draw a dashed line to indicate a potential energy curve for the reaction if a catalyst is added.
  1. Base your answer to the following question on the information below.

A student wishes to investigate how the reaction rate changes with a change in concentration of HCl (aq).

Given the reaction: Zn(s) + HCl (aq)  H2 (g) + ZnCl2 (aq)

Describe the effect of increasing the concentration of HCl(aq) on the reaction rate and justify your response in terms of collision theory.

  1. Explain how a catalyst may increase the rate of a chemical reaction.
  1. According to Reference Table I, the dissolving of which salt is accompanied by the release of energy?

(1) LiBr(2) NH4Cl(3) NaCl(4) KNO3

  1. Based on Reference Table I, which reaction is endothermic?

(1) NaOH(s)  Na+(aq) + OH- (aq)(2) NH4Cl(s)  NH4+(aq) + Cl-(aq)

(3) CO(g) + O2(g)  CO2(g)(4) CH4(g) + 2O2(g)  CO2(g) + 2H2O (l)

  1. The difference between the potential energy of the reactants and the potential energy of the products is

(1) ΔG(2) ΔH (3) ΔS(4) ΔT

  1. Which statement describes characteristics of an endothermic reaction?

(1) The sign of ΔH is positive, and the products have less potential energy than the reactants.

(2) The sign of ΔH is positive, and the products have more potential energy than the reactants.

(3) The sign of ΔH is negative, and the products have less potential energy than the reactants.

(4) The sign of ΔH is negative, and the products have more potential energy than the reactants.

Top View