CHEM 280 MIDTERM EXAM WITH OBJECTIVELY CORRECT QUESTIONS AND ANSWERS

CHEM 280 MIDTERM EXAM WITH
OBJECTIVELY CORRECT
QUESTIONS AND ANSWERS

Identify the abbreviations used for reactants and products used in
chemical reactions. - ANSWERS-g- gas
l- liquid
s- solid
aq- aqueous


1. Given the reaction: 2Li(s) + F2(g)2LiF(s)
What is the correct stoichiometric conversion factor for lithium metal
to fluorine gas?
2. What is the correct stoichiometric conversion factor for lithium
fluoride to fluorine gas?
3. What is the correct stoichiometric conversion factor for lithium
metal to lithium fluoride? - ANSWERS-1. 2mol Li = 1 mol F2
2. 2 mol Li = 1 mol F2
3. 2mol Li = 2 mol LiF


Given the reaction: 2Sr(s) + O2(g) 2SrO(s)
a. If 2 moles of SrO are formed in this reaction, then 2 moles of O2
must have reacted? (True or False)
b. If 2 moles of Sr react, then 2 mol SrO are formed? (True or False)

, c. If 1 mol of O2 react, then 1 mol of Sr react as well? (True or False)
- ANSWERS-a. False: 2 mol SrO = 1mol O2
b. True: 2mol Sr = 2 mol Sro
c. False: 1 mol O2 =2 mol Sr


Given the reaction: 2H2(g) + O2(g) 2H2O(l)
a. How many moles of hydrogen gas are required to make 10.5 moles
of liquid H2O? Assume more than enough oxygen gas?
b. How many moles of liquid water are made from the complete
reaction of 6.6 moles of elemental oxygen gas with more than enough
hydrogen gas? - ANSWERS-


How many moles of aqueous hydrochloric acid are needed to make
4.0 moles of solid gallium chloride?


2Ga(s) + 6HCl(aq) 2GaCl3(s) + 3H2(g) - ANSWERS-4.0 mol GaCl3
x 1mol Fe
/ 2 GaCl3 = 12 mol HCl


Hydrochloric acid can dissolve solid iron according to the reaction:
Fe(s) + 2HCl(aq)FeCl2(aq) + H2(g)


What mass of FeCl2(aq) in grams can be produced by dissolving 25.0
g of solid iron? - ANSWERS-