(a) A reaction in which two or more substances combine to form a single substance is called a................ reaction.(b) A.................. is a substance which changes the rate of a chemical reaction without undergoing a chemical change.(c) The formation of gas bubbles in a liquid during a reaction is called............... (d) The reaction between an acid and a base is called................... (e) Soluble bases are called..............(f) The chemical change involving iron and hydrochloric acid illustrates a..................reaction.(g) In the type of reaction called..................two compounds exchange their positive and negative radicals.................. respectively.(h) A catalyst either................. or................. the rate of a chemical change but itself remains.................... at the end of the reaction.(i) The chemical reaction between hydrogen and chlorine is a............... reaction(j) When a piece of copper is added to silver nitrate solution, it turns................ in color.