Which statements are true? na+ is formed from the reduction of na(s). the oxidation number for is 0. the oxidation number for cu(s) is +2. zn2+ is formed from the oxidation of zn(s). a reducing agent gains electrons. an oxidizing agent gains electrons?

Following are True among given options;

1) The oxidation number for Hg(l) is 0:
                                                            It is correct as Mercury is present in its standard state and has a zero oxidation number.

2) Zn⁺² is formed from the oxidation of Zn (s):
                                                            This statement is correct as an element when looses electron gets positive charge. In this case the oxidation number of Zn has changed from 0 to +2, hence, it has lost 2 electrons and is oxidized.

3) An oxidizing agent gains electrons:
                                                           This statement is correct because Oxidizing agents are those compounds which gains electron from other substance making them oxidized and getting themselves reduced.

Yes, endothermic means it turns cold. and some chemical changes include change of tempature.

Adialysis unit requires 78.5 l of water.the estimated digit is 5.