Chemistry 112
Second Hour Exam
Name:____________
(4 points)
Please show all work for partial credit
All problems worth 14 points. You only have to answer 7 of the 8 questions!
If attempt all 8 I will give you your 7 best scores.
1. A sample of CO2 gas contains 8.45x1024 atoms of carbon.
A. How many moles of CO2 are in his sample?
B. How many grams of CO2 are in this sample?
C. How many atoms of Oxygen are in this sample?
2.
A. What is the difference between a molecular formula and an empirical
formula?
B. What is the difference between atomic mass of an isotope and atomic weight
of an element?
C. What is the difference between % yield and % composition?
D. What is the difference between a complete ionic equation and a net ionic
equation?
E. What is the difference between an oxidation reaction and a reduction
reaction?
2
3. Balance the following reactions:
A. Solid iron(III) sulfide reacts with gaseous hydrogen chloride to produce solid iron(III)
chloride and hydrogen sulfide gas.
B. Aqueous barium hydroxide reacts with aqueous phosphoric acid to form solid barium
phosphate and water.
4. If the % yield in the following reaction is only 25%, how many grams of KOH do I
need to obtain 500g of Fe(OH)3
Fe(NO3)3(aq) + 3KOH(aq) 6 Fe(OH)3(s) + 3KNO3(aq)
3
5. I am going to dissolve 50 grams of aluminum sulfate in 1.5 L of solution. What is the
molarity of aluminum sulfate, aluminum ion and sulfate ion in the final solution?
6. Circle the compounds that you would expect to be soluble in aqueous solution
NaCl
Hg2Cl2
(NH4)3PO4
CaSO4
BeS
Sr(OH)2
Ti(NO3)4
BaI2
Cs2SO4
4
7. Determine the oxidation number for each atom in the following compounds:
KMnO4
K2CrO4
BeF2
NH4NO3
(Determine a separate oxidation number for each N!)
8. Balance the following redox equations
SiCl4(l) + Mg(s) 6MgCl2(s) + Si(s)
(Under acidic conditions)
Fe(s) + O2(g)6 Fe(OH)3
(Under basic conditions)
(Split into following two half reactions: Fe(s)6Fe3+, O2(g)6OH-)