What is the mass, in mg\text{mg}mg, of nitrogen gas (N2\text{N}_2N2) formed when 2.5 × 10-4 mol of ammonia (NH3\text{NH}_3NH3) reacts completely with an excess of copper(II) oxide?
3CuO(s)+2NH3(g)→3Cu(s)+N2(g)+3H2O(l) 3\text{CuO}(\text{s}) + 2\text{NH}_3(\text{g}) \rightarrow 3\text{Cu}(\text{s}) + \text{N}_2(\text{g}) + 3\text{H}_2\text{O}(\text{l}) 3CuO(s)+2NH3(g)→3Cu(s)+N2(g)+3H2O(l)3.5×10−33.5 \times 10^{-3}3.5×10−3
1.75×1001.75 \times 10^01.75×100
3.5×1003.5 \times 10^03.5×100
7.0×1007.0 \times 10^07.0×100
79 exam-style questions on AQA A Level Chemistry Amount of substance, covering Relative atomic mass and relative molecular mass, The mole and the Avogadro constant, The ideal gas equation, Empirical and molecular formula, and Balanced equations and associated calculations. Each one has a worked solution and a mark scheme showing where the marks go.