Task

Sodium hydroxide solution was added stepwise to a solution containing 26.7 g of aluminium chloride: first 0.6 mol, then another 0.1 mol of NaOH. Alkali was then added until the precipitate dissolved completely, and carbon dioxide was passed through the solution until no more precipitate formed. The precipitate was separated and heated. 1) Write the reaction for the first 0.6 mol of NaOH in molecular and ionic form and find the mass of precipitate. 2) Show with an equation what happens on adding another 0.1 mol of NaOH and calculate the remaining precipitate mass. 3) Calculate how much NaOH in total is needed to dissolve the precipitate completely and the corresponding mass of 20 % solution. 4) Write the reaction when CO₂ is passed through the tetrahydroxoaluminate solution and find the required CO₂ volume (L, STP). 5) Write the equation for heating the precipitate and calculate the mass of the solid residue and the mass loss. For every part, show the method (reaction equations, formulas, reasoning) and all calculations step by step.