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.
ScanSolve AI Answer
Here are the solutions to the questions: 14. Complete the following equations. a) H - C C - CH_3(g) + 2H_2(g) Ni or Pt CH_3 - CH_2 - CH_3(g) b) CH_2CH_3 & H \\ & / \\ & C = C \\ / & \\ H & H + HBr → CH_3CH_2 - CHBr - CH_3 c) C_2H_5OH(aq) + HCOOH(aq) HCOOC_2H_5(aq) + H_2O(l) 15. Self raising baking flour contains a mixture of tartaric acid and sodium hydrogen carbonate. State and explain the role of tartaric acid in the mixture. Role: Tartaric acid acts as an acid that reacts with sodium hydrogen carbonate to produce carbon dioxide gas. Explanation: When the flour is mixed with water, the tartaric acid reacts with the sodium hydrogen carbonate (NaHCO_3) to release carbon dioxide gas. This gas gets trapped in the dough, causing it to rise and become light and fluffy during baking. The acid also helps to neutralize the alkaline taste of sodium hydrogen carbonate. 16. The following set-up was used to investigate the percentage of oxygen in air by volume. a) State and explain the observations made when a gas jar is inverted over the burning candle. Observations: The candle flame goes out and the water level inside the gas jar rises. Explanation: The burning candle consumes oxygen from the air inside the gas jar. Once the oxygen is depleted, the flame extinguishes. The carbon dioxide produced by combustion is absorbed by the sodium hydroxide solution. This removal of oxygen and carbon dioxide causes a decrease in the volume of gases inside the jar, leading to a drop in pressure, which in turn causes the water level to rise. b) Theoretical percentage of oxygen in air by volume is 20% while that obtained experimentally may not be 20%. State two possible causes of error. • Incomplete combustion of the candle, meaning not all oxygen is consumed. • Leakage of air into or out of the gas jar during the experiment. • Incomplete absorption of carbon dioxide by the sodium hydroxide solution. • The experiment not being allowed to cool to room temperature before taking the final reading. 17. The apparatus below was used during an experiment. The contents in the apparatus were allowed to mix by tilting it. Sodium iodide solution and Lead nitrate solution. State the observations made when the solutions mix. Explain your answer by use of an equation. Observations: A yellow precipitate is formed. Explanation: Lead(II) nitrate and sodium iodide react in a double displacement reaction to form lead(II) iodide, which is an insoluble yellow solid, and soluble sodium nitrate. Equation: Pb(NO_3)_2(aq) + 2NaI(aq) → PbI_2(s) + 2NaNO_3(aq) 18. Hydrogen and bromine reacting according to the equation: H_2(g) + Br_2(g) = 2HBr(g). Use bond energies given below to calculate the heat of formation of hydrogen bromide. Step 1: Calculate the energy required to break bonds (reactants). Energy to break H-H bond = 436 kJ mol^-1 Energy to break Br-Br bond = 192 kJ mol^-1 Total energy to break bonds = 436 + 192 = 628 kJ mol^-1 Step 2: Calculate the energy released when bonds are formed (products). Energy released by forming 2 H-Br bonds = 2 × 368 kJ mol^-1 = 736 kJ mol^-1 Step 3: Calculate the enthalpy change ( H) for the reaction. H = Energy broken - Energy formed H = 628 kJ mol^-1 - 736 kJ mol^-1 H = -108 kJ mol^-1 This is the enthalpy change for the formation of 2 moles of HBr. Step 4: Calculate the heat of formation for 1 mole of hydrogen bromide ( H_f). H_f (HBr) = ( H)/(2) H_f (HBr) = -108 kJ mol^-12 H_f (HBr) = -54 kJ mol^-1 The heat of formation of hydrogen bromide is: -54 kJ mol^-1 19. The following set-up of apparatus is used to prepare and collect oxygen. a) Identify substance P. Substance P is Manganese(IV) oxide (MnO_2). b) Write an equation for the reaction that takes place in the flask. 2H_2O_2(aq) MnO_2(s) 2H_2O(l) + O_2(g) c) State two physical properties of oxygen gas. • It is a colorless gas. • It is an odorless gas. • It is slightly soluble in water. • It is denser than air. d) State one industrial use of oxygen gas. • Used in welding and cutting metals (e.g., oxy-acetylene torches). • Used in steel making to remove impurities. • Used in medical applications for patients with breathing difficulties. • Used as an oxidizer in rocket fuel. e) Explain why oxygen gas is collected over water. Oxygen gas is collected over water because it is sparingly soluble (or slightly soluble) in water and does not react with