This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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Here are the solutions to the questions: Question 1: A thistle funnel* has a long stem and an open top, used to add liquids to a reaction vessel without a stopcock, often extending below the liquid surface to prevent gas escape. A dropping funnel* has a stopcock to control the rate of liquid addition drop-wise, and its stem typically ends above the liquid surface. Question 2: a) Step 1: Write the balanced chemical equation for the thermal decomposition of lead(II) nitrate. 2Pb(NO_3)_2(s) 2PbO(s) + 4NO_2(g) + O_2(g) b) Nitrogen(IV) oxide (NO_2) can be separated from oxygen (O_2) by cooling the mixture*. At low temperatures, NO_2 dimerizes to form colourless liquid dinitrogen tetroxide (N_2O_4), while oxygen remains a gas. The liquid N_2O_4 can then be separated. Question 3: a) The litmus solution turns red*. b) Sulphur(IV) oxide (SO_2) is an acidic gas. When bubbled through water, it reacts to form sulphurous acid (H_2SO_3), which is acidic and turns litmus red. SO_2(g) + H_2O(l) H_2SO_3(aq) Question 4: a) The method of separation illustrated is Distillation*. b) Mixture M is likely a solution of a non-volatile solid in a liquid or a mixture of two miscible liquids with different boiling points*. c) An application is the purification of water* (separating water from dissolved salts). Question 5: a) When hydrogen sulphide gas is bubbled into concentrated nitric(V) acid: Observation: A yellow precipitate (sulfur) is formed, and brown fumes* (nitrogen dioxide) are observed. Explanation:* Hydrogen sulphide (H_2S) is oxidized to sulfur, while concentrated nitric(V) acid (HNO_3) is reduced to nitrogen dioxide. H_2S(g) + 2HNO_3(aq) S(s) + 2NO_2(g) + 2H_2O(l) b) When hydrogen sulphide gas is bubbled into freshly prepared iron(III) chloride solution: Observation: The brown/yellowish-brown solution turns pale green, and a yellow precipitate* (sulfur) is formed. Explanation:* Iron(III) ions (Fe^3+) are reduced to iron(II) ions (Fe^2+), and hydrogen sulphide (H_2S) is oxidized to sulfur. 2FeCl_3(aq) + H_2S(g) 2FeCl_2(aq) + S(s) + 2HCl(aq) Question 6: a) Water hardness is caused by the presence of dissolved calcium ions (Ca^2+) and magnesium ions (Mg^2+)*. b) One method to remove permanent hardness is the washing soda method* (adding sodium carbonate). c) One advantage of drinking hard water is that it provides essential calcium and magnesium ions* for healthy bones and teeth. Question 7: The sample was pure water*. Reason: The heating curve shows a sharp and constant melting point at 0^ and a sharp and constant boiling point at 100^*. Impure substances melt and boil over a range of temperatures. That's 2 down. 3 left today — send the next one.