Question

Aqueous sulfuric acid

H2SO4

will react with solid sodium hydroxide

NaOH

to produce aqueous sodium sulfate

Na2SO4

and liquid water

H2O

. Suppose 96.1 g of sulfuric acid is mixed with 21. g of sodium hydroxide. Calculate the minimum mass of sulfuric acid that could be left over by the chemical reaction. Be sure your answer has the correct number of significant digits.

Answer 1

molar mass of H2SO4 = 98 g/mol
molar mass of NaOH = 40 g/mol
number of mole = (given mass)/(molar mass)
number of mole of H2SO4 = 96.1/98
= 0.98 mole
number of mole of NaOH = 21/40
= 0.52 mole

reaction taking place is
H2SO4 + 2NaOH -- > Na2SO4 + 2H2O
according to reaction
2 mole of NaOH require 1 mole of H2SO4
1 mole of NaOH require 1/2 mole of H2SO4
0.52 mole of NaOH require (1/2)*0.52 mole of H2SO4
0.52 mole of NaOH require 0.26 mole of H2SO4

number of mole of H2SO4 left = (0.98 - 0.26) mole
= 0.72 mole
mass of H2SO4 left = (number of mole left)*(molar mass)
= 0.72*98
= 70.6 g
= 71 g

Answer : 71 g