can someone explain 5a,5b and 5c i dont get it and why does a precipitate form... i never learn magnesium sulphate + NaOH or H2S04
and for 3a why do you divide by 74.1 and times 10
For 5b, the compound has a carbonate ion provided that it has CO2 gas released. BaSO4 is less soluble than MgSO4 as solubility decreases down Group 2, so it has barium ion. So it is BaCO3.
For 5c, you can find that only compound 4 has no observable change with OH- ion as it has OH- ions itself, so compound 4 is the answer.
For 3a, g/dm3 divided by g/mol is mol/dm3