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DSE化學科 Chemistry 題庫｜十二課題溫習攻略
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20 questions available freeAmmonia is synthesized in the Haber process, involving the following system in equilibrium at temperature T: N₂(g) + 3H₂(g) ⇌ 2NH₃(g) ΔH = -92 kJ mol⁻¹ The pressure is increased by decreasing the volume of the closed container while keeping the temperature at T. Explain whether the yield of ammonia will increase. (2 marks)
Solution X is an aqueous solution of a weak organic base, ethylamine (CH₃CH₂NH₂). Solution X can be neutralized by standard dilute hydrochloric acid to form salt Y. If the neutralization is carried out by titration, suggest a suitable indicator and state the colour change at the end point.
Compound X is a primary alcohol with the chemical formula CH₃CH₂CH₂OH. X is completely oxidized to a carboxylic acid Y by heating with excess acidified potassium dichromate solution under reflux. All the acid Y formed is separated and purified before neutralization with sodium hydroxide solution. Assume complete conversion and no loss during collection. (a) State the IUPAC name of carboxylic acid Y. (1 mark) (b) If 3.6 g of X is completely converted to acid Y, calculate the volume (in cm³) of 0.15 mol dm⁻³ sodium hydroxide solution required to completely neutralize the acid Y formed. (X's molar mass = 60.0 g mol⁻¹) (2 marks)
A glass flask of volume 150 cm³ is completely filled with pure ethanol (C₂H₅OH) at room temperature. Calculate the number of ethanol molecules in the flask. (Density of ethanol at room temperature = 0.789 g cm⁻³; Avogadro's constant = 6.02 × 10²³ mol⁻¹; relative atomic masses: H = 1.0, C = 12.0, O = 16.0)
Sulphur trioxide is manufactured industrially by a process involving the following system in equilibrium at temperature T. 2SO₂(g) + O₂(g) ⇌ 2SO₃(g) : ΔH = -197 kJ mol⁻¹ The pressure is increased by decreasing the volume of the closed container while keeping the temperature at T. Explain the effect on the yield of sulphur trioxide.
A volumetric flask is completely filled with 250.0 cm³ of pure liquid ethanol (C₂H₅OH) at room temperature. Calculate the number of ethanol molecules present in the flask. (Density of ethanol at this temperature = 0.789 g cm⁻³, Avogadro's constant = 6.02 × 10²³ mol⁻¹, relative atomic masses: H = 1.0, C = 12.0, O = 16.0)
A student performed tests on two chemical substances X and Y, and made the following observations. | Test | Observation | | :--- | :--- | | 1: Gas X was passed into an acidified potassium dichromate solution. | The solution turned from orange to green. | | 2: Acidified silver nitrate solution was added to a solution of Y. | A pale yellow precipitate was formed. | Suggest an inorganic gas which could be X. (1 mark)
Methanol can be manufactured by an industrial process involving the following system in equilibrium at temperature T: CO(g) + 2H₂(g) ⇌ CH₃OH(g) : ΔH = -90 kJ mol⁻¹ The pressure is increased by decreasing the volume of the closed container while keeping the temperature at T. Explain whether the yield of methanol will increase.
Methanol can be produced in a closed container by the equilibrium reaction: CO(g) + 2H₂(g) ⇌ CH₃OH(g) ΔH = −90 kJ mol⁻¹ The volume of the container is increased at constant temperature. How does the yield of methanol change when equilibrium is re-established? Explain your answer. (2 marks)
Calculate the number of atoms in 1.0 g of the ²⁴Mg isotope. The mass of one ²⁴Mg atom is approximately 4.0 × 10⁻²³ g. Taking the molar mass of ²⁴Mg as approximately 24 g mol⁻¹, hence estimate Avogadro’s constant.
The diagram above illustrates the apparatus used for the electrolysis of two solutions. Electrode A is made of copper, and the electrolyte in the first cell is copper(II) sulphate solution. Electrodes B, C and D are all made of graphite. P and Q are the poles of the battery. On completion of the circuit, a reddish-brown solid deposits on electrode B, and gas bubbles are observed at electrodes C and D. Write an ionic equation for the reaction occurring at electrode A. State whether the blue colour of the copper(II) sulphate solution will fade after some time, and explain your answer briefly. (3 marks)
The diagram shows a cell used to electrolyse aqueous Z(NO₃)₂. Electrode A is metal Z and electrode B is graphite. A constant current of 2.5 A flows for 12 minutes 52 seconds, depositing 0.654 g of Z on electrode B. Assume that all charge passing through B is used to deposit Z. Calculate the relative atomic mass of Z. Take 1 faraday = 96,500 C mol⁻¹. (3 marks)
Calculate the number of atoms in 1.0 g of the ²⁴Mg isotope. The mass of one ²⁴Mg atom is approximately 4.0 × 10⁻²³ g. Taking the molar mass of ²⁴Mg as approximately 24 g mol⁻¹, hence estimate Avogadro’s constant.
Sulfur trioxide can be manufactured by the Contact process, which involves the following system in equilibrium at temperature T. 2SO₂ (g) + O₂ (g) ⇌ 2SO₃ (g) : ΔH = -197 kJ mol⁻¹ What is the effect of decreasing the temperature on the yield of sulfur trioxide?
For each of the following pairs of oxides: - carbon monoxide and carbon dioxide - sulphur dioxide and sulphur trioxide State the conditions required to convert the lower oxide to the higher oxide.
A student tested two chemical substances X and Y and made the following observations: | Test | Observation | |---|---| | I: Gas X was passed into acidified potassium dichromate solution. | The solution changed from orange to green. | | II: Lead(II) nitrate solution was added to a solution of Y. | A white precipitate was formed. | Suggest two anions in aqueous solution (other than chloride ions) that would form a white precipitate with lead(II) nitrate solution. (2 marks)
Ammonia is manufactured by the Haber process, which involves the following system in equilibrium at a specific temperature T. N₂(g) + 3H₂(g) ⇌ 2NH₃(g) : ΔH = -92 kJ mol⁻¹ Finely divided iron is used as a catalyst in this process. What is the purpose of using a catalyst? Explain what effect the catalyst has on the equilibrium yield of ammonia. (2 marks)
Heating solid ammonium chloride with solid calcium hydroxide produces a colourless gas Y. The diagram shows Y being passed separately into water and methylbenzene (toluene). Name gas Y. (1 mark)
Concentrated sulphuric acid is slowly added to solid sodium chloride. The colourless gas X formed is separately dissolved in water and in methylbenzene (toluene) using an inverted funnel. Some properties of the resulting solutions are listed in the table below. Identify gas X. Explain why the solution of gas X in water conducts electricity while its solution in methylbenzene does not. (3 marks)
A 480 cm³ flask is filled with pure carbon dioxide gas at room temperature and pressure. How many carbon dioxide molecules are in the flask? (Assume the molar volume of a gas at room temperature and pressure = 24.0 dm³ mol⁻¹, Avogadro's constant = 6.02 × 10²³ mol⁻¹)
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根據本題庫其中 1315 條有足夠作答樣本嘅題目、累計 46,267 次真實作答統計，以下選項最多考生揀錯——溫習時特別留神。
1
鋅半電池分別與不同金屬 X 的標準半電池組成原電池，各半電池由惰性鹽橋連接。考慮常規電流在外電路由 X 流向鋅的組合，哪種 X 會產生最大的標準電動勢？ 已知標準還原電位（V）：M…
最多人誤揀：鎂。
61% 作答者揀咗呢個錯誤選項 · 此題累計 38 次作答
2
一份以稀鹽酸酸化的氯化鐵(II)溶液在空氣中放置，直至其中的鐵(II)離子完全被空氣中的氧氣氧化。其後逐滴加入濃氨水至過量。最後留下的沉澱物是甚麼顏色？
最多人誤揀：灰綠色
61% 作答者揀咗呢個錯誤選項 · 此題累計 38 次作答
3
只考慮分子式 C₅H₁₂O 的中性、無環、飽和一元醇。若每個對映異構體分別計算，共有多少種不同異構體？
最多人誤揀：10
57% 作答者揀咗呢個錯誤選項 · 此題累計 35 次作答
4
以下結構為 CH₃CH=CHCH(Cl)CH₂CH₃，含一個碳碳雙鍵和一個手性中心。把每種順反形式及每個對映異構體分別計算，共有多少種不同立體異構體？
最多人誤揀：8
67% 作答者揀咗呢個錯誤選項 · 此題累計 30 次作答
5
以下結構為 CH₃CH=CHCH₂CH₂CH₃。這種化合物共有多少種順反異構形式？
最多人誤揀：4
56% 作答者揀咗呢個錯誤選項 · 此題累計 34 次作答
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