10th Class Physics 1st Lesson Chemical Reactions and Equations Questions and Answers (In Textbook)

10th Class Physics 1st Lesson Chemical Reactions and Equations Questions and Answers (In Textbook)

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Question 1.Why should a magnesium ribbon be cleaned before burning in air ?

Answer: Magnesium ribbon should be cleaned with sand paper before burning in air order to remove white layer of magnesium oxide (MgO) from its surface which hinders the burning of magnesium.

Question 2.Write the balanced equation for the following chemical reactions.

i) Hydrogen + Chlorine → Hydrogen chloride

ii) Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride

iii) Sodium + Water → Sodium hydroxide + Hydrogen

Answer:

i) H2(g) + Cl2(g) → 2HCl2(g)

ii) 3BaCl2(aq) + Al2(SO4)3(aq) → 3BaSO4(s) + 2AlCl3(aq)

iii) 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)

Question 3.Write a balanced chemical equation with state symbols for the following reactions.

i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.

ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.

Answer:

i) BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq)

ii) NaOH(aq) + HCl(aq) → NaCl(aq) + H2O (l)

Question 4.A solution of a substance ‘X’ is used for white washing.

i) Name the substance ‘X’ and write its formula.

ii) Write the reaction of the substance ‘X’ named in (i) above with water.

Answer:

i) For white washing a solution quick lime is used. The substance ‘X’ is quick lime and its formula is CaO (Calcium oxide)

ii) When quick-lime reacts with water, the following reactions takes place.

Question 5. Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other ? Name this gas.

Answer:

During electrolysis, water decomposes to form hydrogen and oxygen gases.

In the above reaction, the balanced chemical equation shows that an electrolysis, the water decomposes to form hydrogen and oxygen in the ratio of 2 : 1 by volume.

Question 6.Why does the colour of copper sulphate solution change when an iron nail is dipped in it ?

Answer:

Iron is more reactive element than copper. When an iron nail is dipped in copper sulphate solution which is blue in colour, iron being more reactive than copper displaces copper from copper sulphate and forms, iron (II) sulphate which is green in colour.

Question 7.Give an example of a double displacement reaction other than the one given in Activity 1.10.

Answer:

AgNO3 (aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)

Question 8.Identify the substances that are oxidised and the substances that are reduced in the following reactions.

i) 4Na(s) + O2(g) → 2Na2O(s)

ii) CuO(s) + H2(g) → Cu(s) + H2O(I)

Answer:

i) Na has gained oxygen and forms Na20. So, Na is oxidised and O2 is reduced.

ii) CuO has lost oxygen and forms Cu. So, CuO is reduced and H2 which has gained oxygen is oxidised.

10th Class Physics 1st Lesson Chemical Reactions and Equations Questions and Answers (In Textbook)