穎新 發問於 科學及數學化學 · 6 年前

Chemistry 溫習題目 7

1. Carbon dioxide was bubled into dilute sodium hydroxide and calcium hydroxide solutions separately.

a) Write chemical equations (with state symbols) for the reactions involved in the experiments.

b) Explain the difference in observations of the two experiments.

c) Suggest a chemical method to show that sodium hydroxide solution has reacted with carbon dioxide. Write a chemical equation for the reaction involved.

2. Limewater is a saturated solution of calcium hydroxide. It is an alkaline solution which can be used as a medicine to treat stomach upset in babies.

a) Suggest how limewater is prepared in the laboratory from solid calcium hydroxide.

b) Name the ion which is responsible for the alkaline properties of limewater.

c) When limewater is warmed with ammonium nitrate solution, a salt, ammonia gas and water are produced. Write an equation for the reaction involved.

d) What would be observed when the following solution is mixed with limewater? Write an ionic equation for the reaction involved.

(i) Sodium carbonate solution

(ii) Copper(II) nitrate solution

1 個解答

評分
  • 土扁
    Lv 7
    6 年前
    最愛解答

    1.

    (a)

    Carbon dioxide with dilute sodium hydroxide :

    2N aOH(aq) + CO2(g) → N a2CO3(aq)+ H2O(l)

    When carbon dioxide is in excess :

    N a2CO3(aq) + CO2(g) + H2O(l) → 2N aHCO3(aq)

    Carbon dioxide with dilute calcium hydroxide :

    2Ca(OH)2(aq) + CO2(g) → CaCO3(s)+ H2O(l)

    When carbon dioxide is in excess :

    CaCO3(aq) + CO2(g) + H2O(l) → Ca(HCO3)2(aq)

    (b)

    Sodium hydroxide : no observable change

    Calcium hydroxide : a white precipitate is formed.

    (c)

    Add a few drops of dilute hydrochloric acid to the resulting solution of the final sodium hydroxide solution. Bubbles of a colourless gas is formed which changes lime water to milky.

    N a2CO3(aq) + 2HCl(g) → 2N aCl(aq) + H2O(l) + CO2(g)

    OR : N aHCO3­(aq) + HCl(aq) → N aCl(aq) + H2O(l) + CO2(g)

    ====

    2.

    (1)

    Add solid calcium hydroxide in a beaker of distilled water, and stir the mixture. Filter off the undissolved solid calcium hydroxide, and the filtrate obtained is limewater.

    (2)

    hydroxide ion

    (3)

    2NH4NO3(aq) + Ca(OH)2(aq) → Ca(NO3)2(aq)+ 2NH3(g) + 2H2O(l)

    (4)(i)

    A white precipitate is formed.

    Ca²⁺(aq) + CO3²⁻(aq) → CaCO3(s)

    (4)(ii)

    A blue precipitate is formed.

    Cu²⁺(aq) + 2OH⁻(aq) → Cu(OH)2(s)

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