write the correct statements:-
1. calcium carbonateand dilute sulphuric acid are used for the preparation of carbon dioxide gas in laboratory.
2. when carbon dioxide gas in excess is passed through lime water, it turns pink.
3. carbon dioxide is used as refrigerant for perishable food.
4. when carbon dioxide gas is passed through Red hot Coke, it forms Oxygen gas.
Answers
1)Dilute sulphuric acid reacts with calcium carbonate. But it is not used because the calcium sulphate which is formed during the reaction is insoluble in water. It covers the marble chips and stops the reaction.
2)hen it reacts with CO2 insoluble CaCO3 is formed which turns solutionmilky. ... When carbon dioxide ispassed through lime water it turns milky due to the formation of waterinsoluble precipitate CaCO3. Still ifexcess of CO2 is passed it formswater soluble Calcium bicarbonate . Thus the solution remains clear.
3)Solid carbon dioxide is also called as dry ice and is commonly used for refrigeration because of its properties. It exhibits a property called as sublimation. In this process a solid changes to gaseous state when exposed to a particular temperature. For dry ice it is -78.5 Celsius .
4)When CO2(g) is passed over red hot coke it partially gets reduced to CO(g). Upon passing 0.5 litre of CO2(g) over red hot coke, the total volume of the gases increased to 700mL.