2.3 g Na is completely burnt to give Na2O,which is then dissolved in 1L. How much H2SO4 in gram is needed to neutralize the solution completely?

2.3———————-X

4Na + O2 = 2Na2O

4(23)—————-2(62)

X = 3.1g

3.1————————-X

Na2O + H2O = 2NaOH

62————————-2(40)

X = 4 g NaOH

4—————X

2NaOH + H2SO4 = Na2SO4 + 2H2O

2(40)———98

X = 4.9 H2SO4

• 2NaOH + H2SO4====> Na2SO4+ 2H2O
• So 80 g of NaOH reacts with 98 g of H2SO4 =
• Therefore 20 g of NaOH will neutralise= 20/80 x 98
• = 24.5 g of H2SO4.
• Here the volume of NaOH or H2SO4 are irrelevant and not required for the question. =÷×=÷×=÷×=÷×=÷×=÷×=÷×=÷×=÷×=÷×=
• To summarize (20/40)= 0.5 Moles of NaOH will react or will be neutralised by (0.5/2)= 0.25 moles of H2SO4 as per the equation.
• So 0.25M H2SO4= 98/4= 24.5 g of H2SO4. Ok.