(1) According to the understanding of common instruments, A is a conical flask and B is an alcohol lamp;
(2) What happens in A is that zinc reacts with dilute hydrochloric acid to generate zinc chloride and hydrogen, and the equation is: Zn+2hcl = zncl2+H2 ↑;
(3) Hydrogen chloride gas is dissolved in water to form hydrochloric acid, which can be neutralized with sodium hydroxide, so the device that can remove a small amount of HCl gas mixed in H 2 is B;
(4) The copper sulfate powder reacts with water to generate blue copper sulfate crystals, so the copper sulfate powder in device E turns blue, indicating that water is generated after the reaction in the hard test tube;
(5) Hydrogen reduction of copper oxide will produce water and copper, so the mass of solid reduction is the mass of oxygen in copper oxide, 5g-4.2g = 0.8g 。
So the mass of copper oxide =4g, then ×100% = 80%;