How many hydrogen atoms are in 4.90 g of ammonium iron(II) sulfate hexahydrate (Mohr's salt), (NH4)2Fe(SO4)2⋅6H2O(\text{NH}_4)_2\text{Fe}(\text{SO}_4)_2\cdot6\text{H}_2\text{O}(NH4)2Fe(SO4)2⋅6H2O (Mr=392.0M_{\text{r}} = 392.0Mr=392.0)?
6.02×10226.02 \times 10^{22}6.02×1022
9.03×10229.03 \times 10^{22}9.03×1022
1.05×10231.05 \times 10^{23}1.05×1023
1.51×10231.51 \times 10^{23}1.51×1023
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.