Solids are heated gently at about 430 K. Select the compound(s) that leave a solid residue of the corresponding normal carbonate.

Answer: B, D

Hydrogencarbonates lose

CO X_{2}

and

H X_{2} O

at this temperature:

2 MHCO X_{3} M X_{2} CO X_{3} + CO X_{2} + H X_{2} O

MgCO X_{3}

and

Li X_{2} CO X_{3}

are normal carbonates that would only lose

CO X_{2}

at much higher temperatures and would give oxides, not carbonates, as residue. So only the Na and K salts are correct.