What is meant by density of a substance?
Use data from the Data Booklet to explain why iron has a greater density than calcium.
Reactions of compounds of transition elements can usually be grouped under one or more of the following headings: acid-base, ligand exchange, precipitation, redox. Select the most suitable heading to describe each of the following reactions by placing a tick ($\checkmark$) in the correct column in the table below. Only one tick should be used for each reaction.
Alloys containing aluminium, titanium and vanadium are used in aerospace and marine equipment, as well as in medicine. When a powdered sample of one of these alloys is heated with excess aqueous NaOH, only the aluminium reacts according to the equation: $2\text{Al}(s) + 2\text{OH}^-(aq) + 6\text{H}_2\text{O}(l) \rightarrow 2[\text{Al}(\text{OH})_4]^-(aq) + 3\text{H}_2(g)$. If $100\,\text{g}$ of alloy is treated in this way, $8.0\,\text{dm}^3$ of hydrogen is collected at room conditions. Calculate the percentage by mass of aluminium in the alloy.