Chemical properties of water
Answers are for parents and teachers.
1
Find the mass of oxygen and of hydrogen in 72 g of water.
72 ÷ 9 = 8, so hydrogen is 8 g and oxygen is 8 × 8 = 64 g.
2
Explain in two sentences why salt dissolves in water.
Water is polar, so its oxygen ends attract Na⁺ and its hydrogen ends attract Cl⁻. The lattice breaks into free hydrated ions.
3
Classify as acidic, basic or neutral in solution: NH₄Cl, Na₂CO₃, NaCl.
NH₄Cl: acidic. Na₂CO₃: basic. NaCl: neutral.
4
Say whether each is acidic, neutral or basic: pH 2, pH 7, pH 10. Which has the most OH⁻?
pH 2 acidic, pH 7 neutral, pH 10 basic; the pH 10 solution has the most OH⁻.
5
Draw a bent water molecule with δ+ and δ− marked, then draw one hydrogen bond to a second molecule.
The oxygen is δ− and the two hydrogens δ+; the dotted line joins the oxygen of one molecule to a hydrogen of the other.