Q50 of 152 Page 22

A silvery-white metal X taken in the form of ribbon, when ignited, burns in air with a dazzling white flame to form a white powder Y. When water is added to powder Y, it dissolves partially to form another substances.

(a) What could metal X be?


(b) What is powder Y?


(c) With which substance metal X combines to form powder Y?


(d) What is substance Z? Name one domestic use of substance Z.


(e) Write a balanced chemical equation of the reaction which takes place when metal X burns in air to form powder Y.

(a) Metal X is Magnesium, Mg.

(b) Powder Y is Magnesium oxide, MgO.


(c) Metal X combines with Oxygen to form powder Y


(d) Substance Z is Magnesium hydroxide, Mg(OH)2; Used as antacid to relieve indigestion.


(e) 2Mg + O2 2MgO



More from this chapter

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48 When metal X is treated with a dilute acid Y, then a gas Z is evolved which bums readily by making a little explosion.

(a) Name any two metals which can behave like metal X.


(b) Name any two acids which can behave like acid Y.


(c) Name the gas Z.


(d) Is the gas Z lighter than or heavier than air?


(e) Is the reaction between metal X and dilute acid Y exothermic or endothermic?


(f) By taking a specific example of metal X and dilute acid Y, write a balanced chemical equation for the reaction which takes place. Also indicate physical states of all the reactants and products.

 49 A solid substance P which is very hard is used in the construction of many buildings, especially flooring. When substance P is heated strongly, it decomposes to form another solid Q and a gas R is given out. Solid Q reacts with water with the release of a lot of heat to form a substance S. When gas R is passed into a clear solution of substance S, then a white precipitate of substance T is formed. The substance T has the same chemical composition as starting substance P.

(a) What is substance P? Write its common name as well as chemical formula.


(b) What is substance Q?


(c) What is gas R?


(d) What is substances? What is its clear solution known as?


(e) What is substance T? Name any two natural forms in which substance T occurs in nature.

 51 A metal X forms a salt XS04. The salt XS04 forms a clear solution in water which reacts with sodium hydroxide solution to form a blue precipitate Y. Metal X is used in making electric wires and alloys like brass.

(a) What do you think metal X could be?


(b) Write the name, formula and colour of salt X S04


(c) What is the blue precipitate Y?


(d) Write a chemical equation of the reaction which takes place when salt XS04 reacts with sodium hydroxide solution. Give the state symbols of all the reactants and products which occur in the above equation.

 52 The metal M reacts vigorously with water to form a solution S and a gas G. The solution S turns red litmus to blue whereas gas G, which is lighter than air, burns with a pop sound. Metal M has a low melting point and it is used as a coolant in nuclear reactors.

(a) What is metal M?


(b) What is solution S? Is it acidic or alkaline?


(c) What is gas G?


(d) Write a balanced chemical equation for the reaction which takes place when metal M reacts with water.


(e) Is this reaction exothermic or endothermic?