What is German silver?

Which of the following is a dibasic acid?

Which metal is purified by the method of liquation?

Metals are refined by using different methods. Which of the following metals are refined by electrolytic refining?
$(i)$ $Au$
$(ii)$ $Cu$
$(iii)$ $Na$
$(iv)$ $K$

Write the electron-dot structure for sodium and chlorine atoms. How do these form a chemical bond? Name the type of bond so formed. Why does a compound so formed have a high melting point?

$(a)$ What type of ores are calcined? Illustrate by giving a suitable example.
$(b)$ In what form is the calcined ore obtained,and how can it be reduced? Give chemical equations of the reduction process involved for the example provided by you.
$(c)$ Name two metals used as reducing agents by displacing metals of lower reactivity from their compounds.