Chemistry 0620 · IGCSE · Identification of ions and gases

Identification of ions and gases — practice question

The table presents the ions found in a $1000\text{ cm}^3$ portion of polluted river water.
(a(i))[1]

Which positive ion has the greatest concentration?

(a(ii))[1]

State the name of the $\text{SO}_3^{2-}$ ion.

(a(iii))[1]

Calculate the mass of silicate ions in $250\text{ cm}^3$ of this sample.

(a(iv))[1]

Calculate the mass of solid obtained when all the water has evaporated from the $1000\text{ cm}^3$ sample.

(a(v))[1]

Name the compound made from $\text{Ca}^{2+}$ ions and $\text{HCO}_3^{-}$ ions.

(b)[2]

Describe a test for sodium ions. test … observation …

(c)[1]

The formulas of several chlorides are shown: aluminium chloride, $\text{AlCl}_3$; calcium chloride, $\text{CaCl}_2$; sodium chloride, $\text{NaCl}$. Deduce the formula of magnesium chloride.

(d)[2]

Molten calcium chloride can be electrolysed with inert electrodes. Predict the products at the negative electrode (cathode) and the positive electrode (anode).

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: sodium / Na⁺

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