CHEM125-C                                                                                                  Fall, 2004

Hourly Exam # 2                                                                                             Dunnivant

 

Name (PRINTED) ____________________________________

 

There are 95 points.  The exam will be graded on a percentage basis.

 

The honor statement must be signed in order for your exam to be graded.

Closed book, closed Internet, closed notes, closed neighbor!

I have neither given nor received aid on this exam.  

                                                            Signature ________________________

 

NOTES:

-Show all work for partial credit.  

-Significant figures and units will be graded throughout the exam.

 

  1. (15pts)  Essay question.  Give an explicit discussion of acid rain.  Explain how it occurs, two major sources, in what types of soils is it a problem, and what toxin results from its presence.  Give ALL reactions of formation for two acids and how the products of these acids react with a soil mineral to neutralize the products of the acids.  When the neutralizing soil mineral is absent show how the toxin is formed.   You must type your answer (in the Hall of Science computer room or on your own computer) and limit your discussion to 1.00 pages.  The equations you use may be handwritten within the 1.00 page limit.  You must turn in a hard copy, not email me a copy.

 

  1. (5pts) List (name) the three basic types of reactions and give an example (balanced reaction) of each.

 

  1. (1 pt each; 10 pts total) Identify which of the following salts are soluble (S) and which are insoluble (I).

 

PbI2  _____

 

Ca3(PO4)2  _____

 

KCl  _____

 

SrSO4  _____

 

CaCO3  _____

 

BaCO3  _____

 

CoS  _____

 

KH2PO4  _____

 

PbCr2O7  _____

 

CaCl2  _____

 

 

  1. (10 pts total) For the following reaction

a)     balance it using the half-reaction concepts used in class (show all work)

b)    give the oxidation state of Fe and Al on both sides of the balanced equation

 

Fe(NO3)2aq  +  Al(s)    Fe(s)  +  Al(NO3)3aq

 

 

  1. (10 pts) A strong acid and a strong base react in a one to one stoichiometry.  For calculation purposes say that the acid is HX with a molecular weight of 50.5 g/mol and the base is YOH with a molecular weight of 45.3 g/mol.  You are to perform a titration where you place the strong base in the beaker or flask and titrate with the strong acid (in the buret).  You place 100.0 mL of an unknown Molarity solution of base in the beaker (flask).  You titrate the base and find that it takes 50.54mL of 0.356M acid to completely neutralize it (the base).  How many grams of base were originally in the flask?

 

  1. (5 pts)  Explain the difference between temperature and heat.

 

  1. (5 pts) If q (heat) > 0 and w (work) > 0 what will be the sign of E?

 

  1. (5 pts) Given the following set of data, why does ammonia and water have a high specific heat?

 

NH3                                   4.70

H2O                                   4.184

Al                                      0.902

glass                                  0.84

 

  1. (10pts) A 45.5 g of metal is heated from 25 oC to 400. oC, how many joules of heat energy must be added to the metal?  (Sp. ht. for the metal = 0.836 J/g-K)

 

  1. (10pts)  A 1.800-g sample of phenol (C6H5OH) was burned in a bomb colorimeter whose total heat capacity is 11.66 kJ/oC.  The temperature of the calorimeter plus contents increased from 21.36 oC to 26.37 oC.  What is the heat of combustion per mole of phenol?

 

  1. (10pts)  Consider the following reaction:

 

CH3OH(g)    CO(g)  +  2H2(g)                        DH = 90.7 kJ

 

a)     Calculate the heat of formation (DHof) of CH3OH.

b)    Calculate the amount of heat generated when 1.60 kg of CH3OH is decomposed by this reaction at constant pressure.

 

DHof  CO =  -110.5 kJ/mol