Calculate the amount of aluminium present in $\text{Al}_2(\text{SO}_4)_3$ if the compound contains 4 g of sulfur.
[Molar mass of sulfur = 32 g/mol , Molar mass of Al =27 g/mol ]

Find the mass of sodium carbonate in grams to form 100 ml 0.1 M solution in water?
( Molar mass of $\text{Na}_2\text{CO}_3$ = 106 g/mol)

What is number of hydrogen molecules needed to synthesize 3.4 g of ammonia by reaction with nitrogen?

What is the approximate mass of the precipitate formed when $50$ mL of $16.9\%$ solution of $\text{AgNO}_3$ is mixed with $50$ mL of $7.45\%$ KCl solution? (Molar mass of $\text{AgNO}_3 = 169$ g/mol, KCl $= 74.5$ g/mol, AgCl $= 143.3$ g/mol)