Sodium hydroxide pellets were accidentally mixed with sodium chloride.7.6g of the mixture were dissolved in water to make one litre of solution.100cm³ of the solution was neutralized by 40cm³ of 0.5M sulphuric(VI)acid.
i)Write an equation for the reaction that took place
ii) Number of moles of the substance in one litre of solution that would react with sulphuric(VI)acid
iii)Mass of unreacted substance in one litre of solution
i) The equation for the reaction that took place is:
NaOH + H2SO4 -> Na2SO4 + H2O
ii) To find the number of moles of the substance in one litre of solution that would react with sulphuric(VI) acid, we first need to determine the number of moles of sulphuric(VI) acid used.
Number of moles of sulphuric(VI) acid = concentration of sulphuric(VI) acid x volume of sulphuric(VI) acid used
Number of moles of sulphuric(VI) acid = 0.5 mol/dm³ x 0.04 dm³
Number of moles of sulphuric(VI) acid = 0.02 moles
Since the reaction between sodium hydroxide and sulphuric(VI) acid is 1:1, the number of moles of the substance in one litre of solution that would react with sulphuric(VI) acid is also 0.02 moles.
iii) To find the mass of unreacted substance in one litre of solution, we need to calculate the number of moles of sodium hydroxide initially present in the mixture.
Number of moles of sodium hydroxide in 7.6g of mixture = mass of mixture / molar mass of sodium hydroxide
Number of moles of sodium hydroxide in 7.6g of mixture = 7.6g / (Na = 22.99g/mol + O = 16.00g/mol + H = 1.01g/mol)
Number of moles of sodium hydroxide in 7.6g of mixture ≈ 0.2 moles
Since the reaction between sodium hydroxide and sulphuric(VI) acid is 1:1, the remaining moles of sodium hydroxide in the solution after neutralization is 0.2 moles – 0.02 moles = 0.18 moles.
To find the mass of unreacted substance in one litre of solution, we calculate the mass of sodium hydroxide corresponding to 0.18 moles.
Mass of unreacted substance in one litre of solution = moles of sodium hydroxide x molar mass of sodium hydroxide
Mass of unreacted substance in one litre of solution = 0.18 moles x (Na = 22.99g/mol + O = 16.00g/mol + H = 1.01g/mol)
Mass of unreacted substance in one litre of solution ≈ 7.07g
Therefore, the mass of unreacted substance in one litre of solution is approximately 7.07g.