A pupil heated 1.24 g of copper carbonate strongly. The chemical reaction which took place is represented by the equation:

CuCO3(s) → CuO(s) + CO2(g)

He then heated the 0.80 g of solid again. When he weighed it after cooling, its
mass was still 0.80 g. Explain why it had not changed in mass this time.

After the solid which remained had cooled, he weighed it.

He found that its mass was 0.80 g.

(i) Why did the pupil find a decrease in mass in this experiment?

Answerthis solution will not form a precipitateexplanationsolubility equilbrium:         pbf₂(s)  ⇄ pb²⁺(aq) + 2 f⁻(aq)the solubility product expression is    (we exclude solids from the equilibrium expression).now suppose we have the trial ion product q, which we can define as    then, we can interpret  q as the product of the concentration of the ions that we have and ksp as the product of the ion concentrations that are needed to form a saturated solution.if q > ksp, then that implies that there will be a surplus of ions that exceed the amount that is required to form a saturated solution. a precipitate will then form (the precipitate continually  forms until the surplus ions are removed and q is decreased to ksp's value).if q = ksp, the saturated solution that forms is barely saturated and the precipitate will be minimal.if q < ksp, then the ion concentration will not be enough to form a saturated solution (so no precipitate).using our information, we calculate the trial ion product:     since q = 2.7  × 10⁻⁸ < ksp =  4  ×  10⁻⁸, a precipitate will not form.

Answerhave membrane-bound organelles;