Science (086) — AI-generated practice question

This is a double displacement reaction (also called a precipitation reaction).

$$\text{Na}_2\text{SO}_4(aq) + \text{BaCl}_2(aq) \rightarrow \text{BaSO}_4(s) + 2\text{NaCl}(aq)$$

It is called a double displacement reaction because the ions of the two reactants exchange (displace) with each other — $\text{SO}_4^{2-}$ ions combine with $\text{Ba}^{2+}$ ions, and $\text{Na}^+$ ions combine with $\text{Cl}^-$ ions. Since one product (BaSO₄) is insoluble and forms a white precipitate, it is also called a precipitation reaction.

Source: Chapter 1, Section 1.2.4 – Double Displacement Reaction

---

• 3 marks = ~3 scorable points: (1) name the reaction type, (2) give the balanced equation, (3) explain why it has that name (ion exchange). Make sure all three are present.
• Examiners expect the term double displacement and the reason: exchange of ions between reactants.
• Mentioning that it is also a precipitation reaction (white, insoluble BaSO₄ forms) can earn the third mark or serve as supporting detail — include it.
• Always write state symbols (aq), (s) in equations; they signal understanding and are expected in board answers.