A substance X, which is an oxide of a group 2 element, is used
intensively in the cement industry. This element is present in bones
also. On treatment with water it forms a solution which turns red
litmus blue. Identify X and also write the chemical reactions involved.
During the reaction of some metals with dilute hydrochloric acid, following observations were made.
(a) Silver metal does not show any change
(b) The temperature of the reaction mixture rises when aluminium (Al) is added.
(c) The reaction of sodium metal is found to be highly explosive
(d) Some bubbles of a gas are seen when lead (Pb) is reacted with the acid.
Explain these observations giving suitable reasons.
Which among the following are physical or chemical changes?
(a) Evaporation of petrol
(b) Burning of Liquefied Petroleum Gas (LPG)
(c) Heating of an iron rod to red hot.
(d) Curdling of milk
(e) Sublimation of solid ammonium chloride
Grapes hanging on the plant do not ferment but after being plucked from the plant can be fermented. Under what conditions do these grapes ferment? Is it a chemical or a physical change?
Ferrous sulphate decomposes with the evolution of a gas having a characteristic odour of burning sulphur. Write the chemical reaction involved and identify the type of reaction.
A solution of potassium chloride when mixed with silver nitrate
solution, an insoluble white substance is formed. Write the chemical
reaction involved and also mention the type of the chemical reaction?
Write the balanced chemical equations for the following reactions
(a) Sodium carbonate on reaction with hydrochloric acid in equal molar concentrations gives sodium chloride and sodium hydrogencarbonate.
(b) Sodium hydrogencarbonate on reaction with hydrochloric acid gives sodium chloride, water and liberates carbon dioxide.
(c) Copper sulphate on treatment with potassium iodide precipitates cuprous iodide (Cu2I2), liberates iodine gas and also forms potassium sulphate.
Identify the oxidising agent (oxidant) in the following reactions
(a) Pb3O4 + 8HCl → 3PbCl2 + Cl2 + 4H2O
(b) 2Mg + O2 → 2MgO
(c) CuSO4 + Zn → Cu + ZnSO4
(d) V2O5 + 5Ca → 2V + 5CaO
(e) 3Fe + 4H2O → Fe3O4 + 4H2
(f) CuO + H2 → Cu + H2O
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