CBSE Class 10 Science Metals and Non metals VBQs Set 04

Question. Which of the following is most reactive with dil. \( H_2SO_4 \)?
(a) Fe
(b) Zn
(c) Cu
(d) Mg
Answer: (d) Mg

Question. Which of the following statement is not correct for \( Zn(s) + CuSO_4(aq) \rightarrow ZnSO_4(aq) + Cu(s) \)?
(a) Zinc is more reactive than Cu
(b) Zn loses electrons to form \( Zn^{2+} \) ion
(c) Zn is lower down the reactivity series as compared to Cu
(d) Zn is strong reducing agent and can reduce \( Cu^{2+} \) to Cu.
Answer: (c) Zn is lower down the reactivity series as compared to Cu

Question. Which of the following metal is extracted by electrolytic reduction of their ores?
(a) Cu
(b) Al
(c) Zn
(d) Hg
Answer: (b) Al

Question. Which type of copper is formed by the reaction:
\( 2Cu_2S + 3O_2 \rightarrow 2Cu_2O + 2SO_2 \)
\( Cu_2S + 2Cu_2O \rightarrow 6Cu + SO_2 \)
(a) Blister copper
(b) Copper cusp
(c) Reduced copper
(d) Copper slag
Answer: (a) Blister copper

In the following Questions, the Assertion and Reason have been put forward. Read the statements carefully and choose the correct alternative from the following:
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.

Question. Assertion: Sulphur is a non-metal.
Reason: Sulphur can gain 2 electrons to form \( S^{2-} \) ion.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
Answer: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

Question. Assertion: Boron and silicon are metalloids.
Reason: \( B_2O_3 \) is more acidic than \( SiO_2 \).
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
Answer: (b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.

Question. The welding of railway tracks is done with help of thermite reaction which involves displacement of a metal (X) from its solid oxide (Y). Identify ‘X’ and ‘Y’ and write chemical reaction involved.
Answer: Metal (X) is Iron (Fe) and the solid oxide (Y) is Iron(III) oxide (\( Fe_2O_3 \)). The thermite reaction involves the reaction between iron(III) oxide and aluminium powder:
\( Fe_2O_3(s) + 2Al(s) \rightarrow 2Fe(l) + Al_2O_3(s) + Heat \)

Question. (a) Why is copper used for making electric wires?
(b) Why do metals form ionic compounds with non-metals?
Answer: (a) Copper is used for making electric wires because it is an excellent conductor of electricity and is highly ductile.
(b) Metals have 1, 2, or 3 valence electrons which they readily lose to achieve a stable octet configuration. Non-metals gain these electrons to complete their octet. This transfer of electrons results in the formation of ionic compounds.

Question. (a) Draw electron dot diagram of \( CaCl_2 \).
(b) Why do ionic compounds have high melting point?
(c) Why is \( CaCl_2 \) soluble in water?
Answer: (a) Calcium loses 2 electrons to form \( Ca^{2+} \) and two chlorine atoms each gain 1 electron to form \( Cl^- \):
\( [Ca]^{2+} [ : \ddot{Cl} : ]_2^- \)
(b) Ionic compounds have high melting points because of the strong electrostatic forces of attraction between oppositely charged ions in the crystal lattice, which require a significant amount of energy to overcome.
(c) \( CaCl_2 \) is soluble in water because it is an ionic compound. Water is a polar solvent that can overcome the lattice energy of the compound, causing the ions to dissociate and become hydrated.

Question. What happens when
(a) Zinc metal is heated with sodium hydroxide.
(b) Ferrous carbonate is heated.
(c) Aluminium strip is added to copper sulphate solution
Write balanced chemical equations for all reactions.
Answer: (a) Zinc reacts with sodium hydroxide to form sodium zincate and hydrogen gas.
\( Zn(s) + 2NaOH(aq) \xrightarrow{\Delta} Na_2ZnO_2(aq) + H_2(g) \)
(b) Ferrous carbonate decomposes on heating to form ferrous oxide and carbon dioxide.
\( FeCO_3(s) \xrightarrow{\Delta} FeO(s) + CO_2(g) \)
(c) Aluminium displaces copper from copper sulphate solution.
\( 2Al(s) + 3CuSO_4(aq) \rightarrow Al_2(SO_4)_3(aq) + 3Cu(s) \)

Question. Complete the following:
(i) \( ZnS + O_2 \rightarrow \)
(ii) \( ZnCO_3 \xrightarrow{heat} \)
(iii) \( HgS + O_2 \rightarrow \)
(iv) \( Al_2O_3 + NaOH \rightarrow \)
(v) \( NaAlO_2 + H_2O \rightarrow \)
Answer:
(i) \( 2ZnS + 3O_2 \rightarrow 2ZnO + 2SO_2 \)
(ii) \( ZnCO_3 \xrightarrow{heat} ZnO + CO_2 \)
(iii) \( 2HgS + 3O_2 \rightarrow 2HgO + 2SO_2 \)
(iv) \( Al_2O_3 + 2NaOH \rightarrow 2NaAlO_2 + H_2O \)
(v) \( NaAlO_2 + 2H_2O \rightarrow Al(OH)_3 + NaOH \)

Question. Alloys are made up of two or more metals. Stainless steel is an alloy of Fe, C, Cr and Ni, used in making utensils and surgical instruments. Duralumin is used for making aeroplanes. Solder is used for soldering electric circuits. Brass and bronze are widely used in daily life. 22 carat gold is used for making jewellery. Diamond is used in jewellery due to its brilliance.
(a) Why is stainless steel preferred over iron and copper for making utensils?
(b) What is the composition of solder?
(c) Which metal is added to gold to make it hard? Calculate % of gold in 22 carat gold.
Answer: (a) Stainless steel is preferred because it is much harder than pure iron, resistant to corrosion (rusting), and does not react with acids in food as copper does.
(b) Solder is an alloy of Lead (Pb) and Tin (Sn).
(c) Copper or silver is added to gold to make it hard.
Percentage of gold = \( \frac{22}{24} \times 100 = 91.67\% \)

Question. Give composition and one use of each of following alloys
(i) Bronze
(ii) Brass
Answer: (i) Bronze: Composition is Copper (Cu) and Tin (Sn). Use: Used for making statues and medals.
(ii) Brass: Composition is Copper (Cu) and Zinc (Zn). Use: Used for making utensils and decorative items.