Experiment 2 (Precipitation of barium (II) sulphate)

In a particular gravimetric analysis, the precipitate of barium sulfate was weighed before it was completely dried. The likely impact of this error on the calculated result is

• a higher result than the correct value.

• minimal, because the mass of water is likely to be very low.

• a lower result than the correct value.

• minimal, because the calculation assumes a hydrated sample is produced.

The best procedure to use when filtering an aqueous solution to collect a precipitate is to ...

• wash the precipitate with a minimal amount of water.

• not wash the precipitate at all.

• use large volumes of water to ensure that all soluble matter is separated from the precipitate.

• warm the solution before filtering.

If 20.0 mL of 0.600 M MgCl2 reacts with 25.0 mL of 0.500 M NaOH, the expected mass of Mg(OH)2 produced is ...

• 0.364 g.

• 0.729 g.

• 0.700 g.

• 1.46 g.

Which of the following is not a property required of the substance chosen for use as a precipitate in a gravimetric analysis?

• Stable when heated to 110°C.

• Low solubility.

• Able to be stored for an extended time without deterioration.

• Has known formula.

A hydrated magnesium salt, MgSO4xH2O, was heated until all the water of hydration was lost. If a 3.188 g sample of hydrated salt produced 1.558 g of anhydrous salt, the value of x in MgSO4xH2O is ...

• 2

• 10

• 5

• 7