
Ore is a deposit in Earth's crust of one or more valuable minerals. The most valuable ore deposits contain metals crucial to industry and trade, like copper, gold, and iron. Copper ore is mined for a variety of industrial uses. Copper, an excellent conductor of electricity, is used as electrical wire.
A phase change is when matter changes to from one state ( solid, liquid, gas, plasma) to another.
That would be the first option Ca(OH)2 + H2SO4 → CaSO4 + 2H2O.
The Ca replaces the H2 in H2SO4, and the H2 replaces the Ca is Ca(OH)2.
Chlorine gas reacts to potassium bromide to form potassium chloride in solution and liquid bromine.
I hope this helps/answers your question! I vaguely remember getting this question before too