The impurity present in the ore is called ..........

(1) gangue
(2) flux
(3) slag
(4) mineral

Silver jewellery turns blacks when exposed to air for long duration. This is due to the formation of : 

(1) Ag₂O 
(2) Ag₂S 
(3) Ag₂O + Ag₃N 
(4) AgN₃

The metal which does not react with cold as well as hot water but reacts with steam is

(1) Cu 
(2) Zn 
(3) Na 
(4) Fe

A metal is strongly heated in presence of air to form a black mass. So the metal is

(1) Potassium
(2) Platinum
(3) Copper
(4) Zinc

Which of the following compounds is bad conductor of electricity?

(1) Ionic compound
(2) Electrovalent compound  
(3) Covalent compound
(4) None of these