CHM 1045 Summer A, 2012
Test 2
Name (print)___________________
Show your work for complete (and partial) credit. Report your answers to the correct
number of significant figures and use units where appropriate. All chemical equations
should balance; indicate phases.
NA=6.022x1023
1. What is the mass of one (average) sodium atom
a) in amu?
b) in grams?
2. a) Give an example of a weak electrolyte(compound name or formula).
b) What is the definition of the mole?
3. Balance the following equation:
____N2O5(g) + ____H2O(l) → ____HNO3(aq)
4. What is the mass of 2.50mol of HCl?
The following information applies to questions 5 and 6.
Compound: CaCl2
Ca(NO3)2 AgCl
AgNO3
f.w.(g/mol): 110.99
164.09
143.321
169.87
CaCl2(aq) + 2AgNO3(aq) → 2AgCl(s) + Ca(NO3)2(aq)
5. How many moles of silver nitrate is required to form 0.845 moles of silver chloride?
6. What mass of CaCl2 is required to form 4.222g of silver chloride?
7.
Compound
Pb(NO3)2
NaI
f.w. (g/mol)
331.2
149.9
Pb(NO3)2(aq) + 2NaI(aq) → PbI2(s) + 2NaNO3(aq)
PbI2
461.0
NaNO3
85.00
1.000g of a mixture of Pb(NO3)2(s) and NaI(s) was added to water and dissolved. A
precipitate of PbI2 was filtered, dried, and weighed. It weighed 0.600g. The limiting
reactant was determined to be NaI. What is the mass percentage of Pb(NO3)2 in the
original sample?
8. When 39.06mg of a hydrocarbon (contains only C and H) was combusted in excess
oxygen, 132.0mg of carbon dioxide and 27.02mg of water formed. What is the empirical
formula for the hydrocarbon? potentially useful information:
Compound/element CO2
O2
H2O
Molar mass (g/mol) 44.009
31.9988
18.015
9. The analysis of an organic compound showed that it contained 0.175 mol of C, 0.140
mol of H, and 0.0350 mol of N. Its molecular mass is about 160. How many
atoms of carbon are there in the empirical formula for the compound and how
many in the molecular formula?
10. (NH4)2C2O4(aq) + CaF2(aq)  CaC2O4(s) + 2NH4F(aq)
Given this equation, indicate the solubility of the following compounds in water. For
each compound, check the appropriate box. If there is not enough information to
determine the solubility, check the last box.
Compound
Soluble Insoluble Not enough info
Ammonium fluoride
Ammonium oxalate
Calcium fluoride
Calcium oxalate
11. Indicate the types of reactions. For each reaction, check the appropriate box. “No
reaction” is a possible response.
Reaction
Precip. Acid/base Ox/red no rxn
H2SO4(aq) + BaCl2(aq)  BaSO4(s) + 2HCl(aq)
H2SO4(aq) + MgCO3(s)  MgSO4(aq) + H2O(l) + CO2(g)
H2SO4(aq) + 2NaCl(aq)  2HCl(aq) + Na2SO4(aq)
H2SO4(aq) + Mg(s)  MgSO4(aq) + H2(g)
12. Predict the products of the following reactions, or write “nr” if no reaction will occur.
Mg is above Al on the activity series. Predict the products, or write “n.r.” if no
reaction will occur.
a) 3MgCl2(aq) + 2AlCl3(aq) 
b) 3Mg(s) + 2AlCl3(aq) 
c) 3MgCl2(aq) + 2Al(s) 
d) 3Mg(s) + 2Al+3(aq) 
13. Given that magnesium is above hydrogen on the activity series, write the net ionic
equation for the spontaneous reaction that occurs between hydrochloric acid (HCl)
and magnesium metal. (balanced; phases)
14. Write the chemical equation for the reaction that occurs when dimethyl ether
(CH3OCH3) is combusted.
15. Write a reduction half reaction. Any reduction half reaction will do.
16. What volume of 1.22M H2SO4 ( 98.08g/mol) would be required to react with 16.0g
of CaCO3(100.09g/mol) according to the following reaction?
CaCO3(s) + H2SO4(aq) → CO2(g) + H2O(l) + CaSO4(aq)
17. What volume of 1.25M CaCl2 is required to react with 14.66mL of 2.50M
AgNO3(aq)? rxn: CaCl2(aq) + 2AgNO3(aq) → 2AgCl(s) + Ca(NO3)2(aq)
18. What volume of 17.0M HCl must be diluted to prepare 450.mL of .250M HCl?
19. If 70.mL of 1.25M CaCl2(aq) is mixed with 125mL of 1.30M AgNO3(aq), what is
the maximum yield of AgCl(s) in grams?
5 points extra credit: What can be deduced concerning the relative positions of
aluminum and zinc on the activity series based on the following "no reaction"?
Please justify your answer. How do you know?
Zn(s) + AlCl3(aq) → n.r.