CHEMICAL REACTIONS AND EQUATIONS
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- Why should a magnesium ribbon be cleaned before burning in air?
- Write a balanced chemical equation for the following reaction:
(a) Hydrogen gas combines with nitrogen to form ammonia. - Write a balanced chemical equation with the state symbols for the following reactions:
(a) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and a solution of sodium chloride.
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4. A solution of a substance 'X' is used for whitewashing.
(a) Name the substance 'X' and write its formula.
(b) Write the reaction of the substance 'X' with water.
5. Why is the amount of gas collected in one of the test tubes in Activity 1.7 (electrolysis of water) double the amount collected in the other? Name this gas.
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6. Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
7. Give an example of a double displacement reaction other than the one given in the text.
8. Identify the substances that are oxidised and the substances that are reduced in the following reaction:
CuO + H₂ → Cu + H₂O
Exercise Questions
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- Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
- Give an example of a double displacement reaction other than the one given in the text.
- Identify the substances that are oxidised and the substances that are reduced in the following reaction:
Fe₂O₃ + 2Al → 2Fe + Al₂O₃ - What is a balanced chemical equation? Why should chemical equations be balanced?
- Translate the following statements into chemical equations and then balance them:
(a) Hydrogen gas combines with nitrogen to form ammonia.
(b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas. - Balance the following chemical equations:
(a) HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + H₂O
(b) NaOH + H₂SO₄ → Na₂SO₄ + H₂O
(c) NaCl + AgNO₃ → AgCl + NaNO₃
(d) BaCl₂ + H₂SO₄ → BaSO₄ + HCl - Write the balanced chemical equation for the following and identify the type of reaction in each case:
(a) Potassium bromide (aq) + Barium iodide (aq) → Potassium iodide (aq) + Barium bromide (s)
(b) Zinc carbonate (s) → Zinc oxide (s) + Carbon dioxide (g)
(c) Hydrogen (g) + Chlorine (g) → Hydrogen chloride (g)
(d) Magnesium (s) + Hydrochloric acid (aq) → Magnesium chloride (aq) + Hydrogen (g) - A shiny brown-coloured element 'X' on heating in air becomes black in colour. Name the element 'X' and the black-coloured compound formed.
- Why do we apply paint on iron articles?
- Oil and fat-containing food items are flushed with nitrogen. Why?
- Explain the following terms with examples:
(a) Corrosion
(b) Rancidity
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