Question

(a) Which metal is extracted from bauxite ore ?
(b) Give the name of one ore of iron. Which iron compound is present in this ore ? Write its chemical formula.
(c) Describe the extraction of zinc metal from its sulphide ore (zinc blende). Write equations of the reactions involved.
(d) Explain why, the galvanised iron article is protected against rusting even if the zinc layer is broken.
(e) Name a common metal which is highly resistant to corrosion.

Lakhmir Singh Chemistry Class 10

Answer 1

: (i) Arrange Cu, Ca, Al, Fe, Mg, Pb, Na and Zn in the decreasing order, in which they appear in the activity series; putting down the most reactive metal first and least reactive in the last.
(ii) (a) Among the above metals, write the names of metals which will displace hydrogen from water or steam.
(b) Give two evidences to show that magnesium is more reactive than iron.
Answer: (i) The given metals are arranged in the activity series of metals as follows: Na, Ca, Mg, Al, Zn, Fe, Pb (most reactive) and Cu (least reactive)
(ii) (a) (1) Sodium and calcium displace hydrogen from cold water.
2Na + 2H2O ⟶ 2NaOH + H2 ↑
Ca + 2H2O ⟶ Ca(OH)2 + H2↑
(2) Magnesium and zinc metals are less reactive as they react with boiling water to liberate hydrogen gas.
Mg + 2H20 ⟶ Mg(OH)2 + H2↑
Zn + 2H20 ⟶ Zn(OH)2 + H2↑
(3) Iron which is less reactive, reacts in red hot conditions with steam to liberate hydrogen gas.
3Fe + 4H20 ⟶ Fe3O4 + 4H2↑
(4) Lead and copper almost fail to liberate hydrogen gas in any conditions, because they are not so reactive. They lie just above and below hydrogen in activity series of metals.
(b) (1) Magnesium reacts with boiling water to liberate hydrogen gas, while iron can do so with steam in red hot condition only.
(2) Magnesium can displace hydrogen from acids vigorously in cold but iron displaces hydrogen slowly.

Question 2: (i) Na, Ca, Mg, Al, Zn, Fe, Pb and Cu, are well known metals.
(a) X, Y and Z are coded letters for three of the metals in the activity series of metals as given above,
Metal X, reacts violently with cold water and its hydroxide is not decomposed by heat.
Metal Y, has no reaction with water but its hydroxide decomposes, with slight warming, giving a black powder.
Metal Z, reacts vigorously with dilute hydrochloric acid but hardly at all with cold water. If it is heated in steam, a white solid A is formed and a colourless gas B is set free
(1) which of the metals in the list is X ?
(2) which of the metals in the list is Y ?
(3) which of the metals in the list is Z ?
(4) Write the name of the solid A and gas B.
(b) State whether the following are soluble or insoluble in water.
(1) The carbonate of X.
(2) The carbonate of Y.
(3) The hydroxide of Z.
(ii) A certain metal does not liberate hydrogen from dilute sulphuric acid but it displaces silver from aqueous silver nitrate solution. State the most likely place for the metal in the activity series.
(iii) What would you expect to happen, if aluminium metal is heated with iron (III) oxide ? Also write the equation.
Answer: (i) (a) (1) The metal X is sodium.
(2) The metal Y is copper.
(3) The metal Z is magnesium.
(4) The name of the solid A is magnesium hydroxide, while the gas B is hydrogen.
(b) (1) Soluble as sodium carbonate is soluble in water.
(2) Insoluble, as copper carbonate is insoluble in water.
(3) Soluble, as magnesium hydroxide is soluble in water.
(ii) The metafiles below hydrogen and above silver in the activity series of metals.
(iii) When aluminium metal is heated with iron (III) oxide with metallic iron, an enormous amount of heat is produced due to the exothermic nature of the reaction. Molten iron is thus produced, which can be used in welding.
Fe2O3 + 2Al ⟶ Al2O3 + 2Fe + Q.

Question 3: (i) Arrang