How many hydrogen atoms are in 4.97 g of nickel(II) acetate tetrahydrate, Ni(CH3COO)2⋅4H2O\text{Ni}(\text{CH}_3\text{COO})_2\cdot4\text{H}_2\text{O}Ni(CH3COO)2⋅4H2O (Mr=248.7M_{\text{r}} = 248.7Mr=248.7)?
(Use Avogadro's constant, NA=6.02×1023 mol−1N_{\text{A}} = 6.02 \times 10^{23}\text{ mol}^{-1}NA=6.02×1023 mol−1)
1.20×10221.20 \times 10^{22}1.20×1022
7.22×10227.22 \times 10^{22}7.22×1022
9.62×10229.62 \times 10^{22}9.62×1022
1.68×10231.68 \times 10^{23}1.68×1023
199 exam-style questions on OCR A A Level Chemistry Atoms and reactions, covering Atomic structure and isotopes, Compounds, formulae and equations, Amount of substance, Acids, and Redox. Each one has a worked solution and a mark scheme showing where the marks go.