Question

1. which ion combination forms a soluble compound with sulfate (so₄²⁻)?

a. na⁺ (sodium)
b. ca²⁺ (calcium)
c. ba²⁺ (barium)
d. pb²⁺ (lead)

Explanation:

Using solubility rules for ionic compounds: sulfates are generally soluble, but exceptions include salts with $Ca^{2+}$, $Ba^{2+}$, $Pb^{2+}$. Salts containing group 1 cations like $Na^+$ are always soluble, so sodium sulfate ($Na_2SO_4$) is soluble in water.

Answer:

a. $\text{Na}^+$ (sodium)