If the crucible wasn't covered with a lid the reactants may have produced a gas that was released into the surroundings, or mass may have been lost in the form of water vapour.
Answer:
0.0250 g.
Explanation:
∵ no. of moles (n) = mass / molar mass.
<em>∴ mass of Vitamine C = (n)(molar mass)</em> = (0.000142 mol)(176.12 g/mol) = 0.02501 g = <em>0.0250 g. "three significant figures"</em>