Quantitative Chemistry

(Topic Questions and Problems)




Consider 10 g of the compound formic acid. It has a molecular formula CH2O2. Answer the following:

a) How many moles of formic acid?

b) How many moles of carbon?

c) how many moles of hydrogen?

d) How many moles of oxygen ?

e) How many carbon atoms ?

f) How many hydrogen atoms ?

g) How many oxygen atoms ?

h) How many total moles of atoms ?

i) how many total atoms ?


What is the mass of 2.500x10^+25 molecules of methanol (CH4O) ?

What is the molecular weight of Aspirin (acetylsalysylic acid: C9H8O4).

What is the percent composition of C, H and O in Aspirin (see problem 3 above).

Lactic acid contains C, H and O atoms. The mass percentage of these atoms is C: 40%, H: 6.7%, 53.3%. The molecular weight of lactic acid is 90 g/mol.

a) What is the emprical formula of lactic acid?
b) What is the molecular formula of lactic acid?

Lead metal is obtained from the mineral lead sulfide through the following reaction:

2PbS(s) + 2C(s) + 3O2(g) ---> 2Ps(s) +2CO(g) + 2SO2(g)

a) If 100 g of PbS is reacted with excess C and O2 what mass of lead metal will be obtained?
b) Suppose 100 g of PbS is reacted with 4g of C and excess O2.
i) What is the limiting reactant?
ii) What mass of lead metal will be obtained?
c) What mass of oxygen is needed to produce 500 g of lead metal?


Hydrogen and oxygen gas react to form water:

2H2(g) + O2(g) ---> H2O(l)

This reaction is exothermic and releases -285.8 kJ of heat. How much heat will be released if10 g of H2(g) is reacted with excess oxygen?

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C101 Class Notes
Prof. N. De Leon