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question_answer1) Hydrogen is regarded as a rogue element in the periodic table. Explain.
question_answer2) Elemental hydrogen reacts with other substances only slowly at room temperature. Why?
question_answer3) Give one example of a reaction in which dihydrogen acts as a reducing agent and an oxidising agent.
question_answer4) Why is dihydrogen gas not preferred in balloons?
question_answer5) Account for the following in the preparation of \[{{H}_{2}}{{O}_{2}}\] from barium peroxide \[(Ba{{O}_{2}})\] and dilute \[{{H}_{2}}S{{O}_{4}}\]. (a) A thin paste of hydrated barium peroxide is used instead of anhydrous peroxide. (b) The temperature of the reaction mixture is kept at 0°C. (c) The final solution must be kept slightly acidic.
question_answer6) Presence of water is avoided in the preparation of \[{{H}_{2}}{{O}_{2}}\] from \[N{{a}_{2}}{{O}_{2}}\]. Assign reason.
question_answer7) Explain the following : (i) Temporary hard water becomes soft on boiling. (ii) Water can extinguish most fires but not petrol fire. (iii) Hard water is softened before being used in boilers.
question_answer8) Hydrogen peroxide is used to restore the colour of old oil paintings containing lead oxide. Explain.
question_answer9) Why are the melting and boiling points of heavy water more than those of ordinary water?
question_answer10) A mixture of hydrazine, hydrogen peroxide and Cu(II) catalyst is used as rocket fuel. Why?
question_answer11) Is it possible to remove completely the temporary hardness due to \[Mg{{(HC{{O}_{3}})}_{2}}\] by boiling?
question_answer12) Is it correct to say that hydrogen can behave as metal? State the condition under which such behaviour is possible.
question_answer13) Elements with atomic numbers 17 and 20 form compounds with hydrogen. Write the formulae of the two compounds and compare their chemical behaviour in water.
question_answer14) Compare the chemical properties of\[{{H}_{2}}O\] and\[{{H}_{2}}{{O}_{2}}\].
question_answer15) What are the advantages of using hydrogen as a fuel?
question_answer16) Why is ice less dense than water? What types of attractive forces must be overcome to melt ice?
question_answer17) Explain why phosphoric acid is preferred to sulphuric acid in the preparation of \[{{H}_{2}}{{O}_{2}}\] from hydrated barium peroxide.
question_answer18) Hydrogen peroxide acts both as an oxidising agent and as reducing agent in alkaline solution towards certain first row transition metal ions. Illustrate both these properties of \[{{H}_{2}}{{O}_{2}}\] using chemical equation.
question_answer19) Why cannot water be used to extinguish petrol fire?
question_answer20) Which isotope of hydrogen is used as a tracer in organic reactions.
question_answer21) Name one example of a reaction in which dihydrogen acts (i) as an oxidising agent and (ii) as a reducing agent.
question_answer22) Name one reaction in which water acts (i) as an oxidising agent and (ii) as a reducing agent.
question_answer23) When \[{{H}_{2}}{{O}_{2}}\] is added to blood, rapid evolution of a gas occurs. Explain.
question_answer24) Presence of water is avoided in the preparation of \[{{H}_{2}}{{O}_{2}}\] from \[N{{a}_{2}}{{O}_{2}}\]. Explain.
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