Practice problem chap3
1. The atomic mass of Cl (75.53%) and 37Cl (24.47%) are 34.968amu and 36.956amu.Calculate
the average atomic mass in amu.
2. What is the mass percent (%) for O in SO2?
(a) 38.09
(b) 45.41
(c) 50.00
(d) 53.86
(e) 56.43
3. How many molecules of ethane (C2H6) are present in 0.334g of C2H6?How many H atoms?
4. Chemical analysis shows the composition of a compound containing carbon and hydrogen, to
be 80.00% carbon and 20% hydrogen and the molar mass is 30 g. What is its molecular formula?
(a) CH
(b) C2H4
(c) C2H6
(d) C6H12
(e) C10H22
5. Balance the equation
a) N2O5  N2O4 +O2
f) P4O10 + H2O  H3PO4
h) Al +H2SO4  Al2(SO4 )3+ H2
j) CH4 + O2 CO2 + H2O
k) Be2C + H2O  Be(OH)2 +CH4
n) NH3 +CuO  Cu + N2 + H2O
6. In the reaction of Al(OH)3 with H2SO4, how many moles of water can be produced If the
reaction is begun with 5.500 mole of Al(OH)3?
2Al(OH)3 + 3H2SO4  Al2(SO4)3 + 6H2O
(a) 2.50
(b) 4.75
(c) 6.32
(d) 7.58
(e) 16.50
7. How many grams of H2O could be formed by the reaction of 16.0 g of CH4 with 48.0 g of O2?
CH4 + 2O2  CO2 + 2H2O
(a) 27.0
(b) 37.3
(c) 46.8
(d) 54.1
(e) 58.78. What is the excess
reagent in the above reaction (Q.23)of CH4 and O2? How many grams of the excess reagent were
consumed?
(a) CH4, 12 grams
(b) O2, 12 grams
(c) CH4, 4 grams
(d) O2, 4 grams
(e) CH4, 8 grams
9. A 31.2 grams of benzene (C6H6) is mixed with excess HNO3 to prepare nitrobenzene
(C6H5NO2). After the reaction there are 38.7 grams of nitrobenzene produced. What is the
percent yield of nitrobenzene?
C6H6 + HNO3  C6H5NO2 + H2O
(a) 34.3%
(b) 47.6%
(c) 58.9%
(d) 63.4%
(e) 71.2%
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