Chemistry: Concentration of sulphuric acid?

Question

25 mls of caustic soda ( containing 10g/dm^3) are exactly sufficient to completely react with 15 mls of sulphuric acid. What was the concentration of the sulphuric acid?

Answer 1

dm^3= 1 liter = 1000ml.

Caustic soda is NaOH, moles of NaOH in 10 g= mass/mass number= 10/40= 0.25

Construct a neutralization equation:

H2SO4 + 2NaOH ==> Na2SO4 + H2O

Moles of NaOH= Volume * Concentration= 0.25 * 25/1000= 0.00625 moles.

Look at the mole ratio of NaOH : H2SO4, its 2:1. So 2 moles of NaOH react with 1 mol of H2SO4. 9.00625 moles of NaOH reacts completely with 0.003125 moles of H2SO4.

Again, concentration= moles/volume= 0.003125/15 * 1000= 2.0833 mol.dm^3.

Hope you understand

Answer 2

Sulfuric acid created by John Roebuck's process only approached a 35–40% concentration.  

Answer 3

2NaOH + H2SO4 ==> Na2SO4 + 2H20

Calculate molarity of NaOH, then calculate # moles used in 25 mls.  The number of moles of H2SO4 will half that number.  Divide that by 0.015 liters to get the molar concentration of H2SO4.