NTSE MAT Class 8 Chemistry Questions and Answers Set A

Question. If Zinc displaces Copper from Copper Sulphate solution, this indicates that
(a) Zinc is more reactive than Copper
(b) Copper is more reactive than Zinc
(c) Both Copper & Zinc are equally reactive
(d) Copper Sulphate is unstable
Answer: (a) Zinc is more reactive than Copper
A more reactive metal can displace a less reactive metal from its solution

Question. In the following reaction \( H_2S_{(aq)} + Br_{2(aq)} \rightarrow 2HBr_{(aq)} + S \)
(a) \( Br_2 \) is an oxidizing agent
(b) \( Br_2 \) is a reducing agent
(c) \( H_2S \) is an oxidizing agent
(d) Both (b) & (c)
Answer: (a) \( Br_2 \) is an oxidizing agent
Since \( Br_2 \) is getting reduced by gaining Hydrogen or electrons it is an oxidising agent.

Question. Black coating formed on the surface of silver articles upon prolonged exposure to air is
(a) Silver Sulphide
(b) Silver Chloride
(c) Silver Carbonate
(d) Silver Sulphate
Answer: (a) Silver Sulphide
\( 2Ag + H_2S \rightarrow Ag_2S + H_2 \)

Question. \( xNH_3 + yCuO \rightarrow aCu + bN_2 + cH_2O \)
(a) 2, 3, 3, 1, 3
(b) 2, 3, 3, 3, 1
(c) 2, 3, 3, 2, 3
(d) None of the options
Answer: (a) 2, 3, 3, 1, 3

Question. Which of thf following is a dibasic acid?
(a) \( HCl \)
(b) \( H_3PO_4 \)
(c) \( H_2SO_4 \)
(d) \( HNO_3 \)
Answer: (c) \( H_2SO_4 \)
\( H_2SO_4 \) as it has two lomsable hydrogen atoms.

Question. \( NH_4Cl \) is a salt of -
(a) Strong acid and strong base
(b) Strong acid and weak base
(c) Weak acid & weak base
(d) Weak acid & strong base
Answer: (b) Strong acid and weak base
\( HCl \) is a strong acid and \( NH_4OH \) is a weak base.

Question. pH of 0.001 M \( HCl \) is –
(a) 4
(b) 2
(c) 1
(d) 3
Answer: (d) 3
\( pH = -\log_{10} [H^+] \)
\( = -\log_{10} [0.001] \)
\( = -\log_{10} 10^{-3} \)
\( pH = 3 \)

Question. When Ethanoic acid is heated with \( NaHCO_3 \), the gas evolved is –
(a) \( H_2 \)
(b) \( CO_2 \)
(c) \( CH_4 \)
(d) \( CO \)
Answer: (b) \( CO_2 \)
\( CH_3COOH + NaHCO_3 \rightarrow CH_3COONa + H_2O + CO_2 \uparrow \)

Question. Oils on treating with hydrogen in the presence of palladium or nickel catalyst form fats. This is an example of-
(a) Addition reaction
(b) Substitution reaction
(c) Displacement reaction
(d) Oxidation reaction
Answer: (a) Addition reaction
Oils arc unsaturated compounds on addition of Hydrogen they get converted into fats which are saturated compounds.

Question. Cinnabar is an ore of –
(a) \( Hg \)
(b) \( Cu \)
(c) \( Pb \)
(d) \( Zn \)
Answer: (a) \( Hg \)
Cinnabar is an ore of mercury (HgS).

Question. Beakers A, B and C contains Zinc sulphate, Silver nitrate and Iron (II) sulphate solution respectively. Copper pieces are added to each beaker. Blue colour will appear in case of –
(a) Beaker A
(b) Beaker B
(c) Beaker C
(d) All the beakers
Answer: (b) Beaker B
In Beaker B Silver Nitrate aqueous solution is there. As we know copper is more reactise as compared to silver it will displace silver from its salt solution and hence, colour of solution will become blue.
\( Cu + 2AgNO_{3(aq)} \rightarrow \underset{\text{Blue colour solution}}{Cu(NO_3)_2} + 2Ag \)

Question. The following equation represents the process of:
\( 2CuS(s) + 3O_{2(g)} \rightarrow 2Cu_2O_{(s)} + 2SO_{2(g)} \)
(a) Calcination
(b) Reduction
(c) Roasting
(d) Decomposition
Answer: (c) Roasting
Roasting is a process where sulphide ores are heated in excess of air to convert it into metal oxide.

Question. Which of the following metals is extracted only by electrolysis?
(a) \( Zn \)
(b) \( Al \)
(c) \( Fe \)
(d) \( C \)
Answer: (b) \( Al \)
\( Zn \) – Blast furnace
\( Fe \) – Blast furnace
\( Cu \) – Bessemerization
\( Al \) – Electrolysis

Question. Which of the following are not ionic compounds?
(i) \( KCl \) (ii) \( HCl \) (iii) \( CCl_4 \) (iv) \( NaCl \)
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (ii) and (iv)
Answer: (b) (ii) and (iii)
H – Cl and C – Cl bonds are covalent bonds.

Question. Which of the following gives the correct increasing order of the atomic radii of O, F and N?
(a) O, F, N
(b) N, F, O
(c) O, N, F
(d) F, O, N
Answer: (d) F, O, N
Order of atomic radius
FLOLN

Question. Solid \( CO_2 \) is stored under –
(a) Low pressure
(b) High pressure
(c) Moderate pressure
(d) Normal atmospheric pressure
Answer: (b) High pressure
High pressure ensures solid state of Carbon dioxide Lowering of pressure will cause the solid to change into the gaseous state (Solid Carbon dioxide is a sublimate substance)

Question. The boiling point of water on Celsius and Kelvin scale respectively is –
(a) 373, 273
(b) 0, 273
(c) 273, 373
(d) 100, 373
Answer: (d) 100, 373

Question. A mixture or Kthanol and water can he separated by-
(a) Filtration
(b) Decantation
(c) Fractional distillation
(d) Sublimation
Answer: (c) Fractional distillation
Mixture of ethanol and water can be separated due to difference in their boiling points
Boiling point of ethanol is \( 78^\circ C \) and boiling point of water \( = 100^\circ C \).

Question. Which of the following are chemical changes?
(i) Decaying of wood
(ii) Burning of wood
(iii) Sawing of wood
(iv) Hammering of a nail into a piece of wood.
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)
Answer: (a) (i) and (ii)
Chemical changes are irreversible in nature and new products are formed in a chemical change. When wood is sawed, or when a nail is hammered into wood, no new substance is formed.

Question. Which of the following is an example of gel?
(a) Coloured gem
(b) Jelly
(c) Smoke
(d) Shaving cream
Answer: (b) Jelly
Gel is a colloid of solid dispersed in liquid Jelly is made by warming and then cooling a liquid containing gelatin or a similar setting agent.

Question. Match the names of the scientists given in column – I with their contributions towards the understanding of the atomic structure as given in column – II and choose the correct option from the codes given below:

(a) (P) – (ii), (Q) – (iv), (R) – (i), (S) – (iii)
(b) (P) – (ii), (Q) – (i), (R) – (iv), (S) – (iii)
(c) (P) – (iv), (Q) – (ii), (R) – (i), (S) – (iii)
(d) (P) – (iii), (Q) – (iv), (R) – (i), (S) – (ii)
Answer: (a) (P) – (ii), (Q) – (iv), (R) – (i), (S) – (iii)

Question. How many molecules are present in 9 g of water?
(a) \( 3.01 \times 10^{23} \)
(b) \( 6.022 \times 10^{23} \)
(c) \( 6.08 \times 10^{23} \)
(d) \( 3.82 \times 10^{23} \)
Answer: (a) \( 3.01 \times 10^{23} \)
18 g water contain \( 6.023 \times 10^{23} \) molecules
9 g water will contain \( \frac{6.023 \times 10^{23} \times 9}{18} = 3.0115 \times 10^{23} \) molecules

Question. Mass of one Avogadro’s number of O atoms is equal to –
(a) 16 amu
(b) 16 g
(c) 32 g
(d) 6 kg
Answer: (b) 16 g
1 Avogadro number \( \equiv \) 1 mole O atoms \( \equiv \) Atomic mass of O atoms

Question. The currect formula of Aluminium Sulphate is –
(a) \( AlSO_4 \)
(b) \( Al_2SO_4 \)
(c) \( Al_3(SO_4)_2 \)
(d) \( Al_2(SO_4)_3 \)
Answer: (d) \( Al_2(SO_4)_3 \)
Valency of Al is 3 & that of sulphate ion \( (SO_4^{2-}) \) is 2, so the molecular formula of compound \( Al_2(SO_4)_3 \).

Question. The formula of the sulphate of an element X is \( X_2(SO_4)_3 \). The formula of nitride of element X will be:
(a) \( X_2N \)
(b) \( XN_2 \)
(c) \( XN \)
(d) \( X_2N_3 \)
Answer: (c) \( XN \)
In \( X_2(SO_4)_3 \), Valency of \( X = 3 \)
Nitride ion \( \equiv N^{3-} \)
\( \therefore \) So, formula of nitride of X = XN

Question. The number of molecules in 16.0 g of oxygen gas is:
(a) \( 6.02 \times 10^{23} \)
(b) \( 6.02 \times 10^{-23} \)
(c) \( 3.01 \times 10^{-23} \)
(d) \( 3.01 \times 10^{23} \)
Answer: (d) \( 3.01 \times 10^{23} \)
Oxygen gas \( = O_2 \)
Molecular mass of this gas \( = 16 \times 2 = 32 \) g
32 g \( O_2 \) has \( 6.023 \times 10^{23} \) molecules of \( O_2 \)
So, 16g \( O_2 \) has \( \frac{6.023 \times 10^{23} \times 16}{32} = 3.011 \times 10^{23} \) molecules.

Question. Which of the following is not correct according to Dalton’s atomic theory?
(a) Matter is made up of atoms
(b) Atoms of all substances arc identical in all respects
(c) Atoms combine in a simple whole number ratio.
(d) Atoms of two elements can combine lo form more than one compound
Answer: (b) Atoms of all substances are identical in all respects
According to Dalton’s atomic theory – atoms of same element are identical in all respects & atoms of different elements are non – identical.

Question. The electron distribution in Aluminium atom is-
(a) 2, 8, 3
(b) 2, 8, 2
(c) 8, 2, 3
(d) 2, 3, 8
Answer: (a) 2, 8, 3
Atomic number of \( Al \equiv 13 \)
Electronic configuration = 2, 8, 3

Question. The mass number of an anion, \( X^{3-} \) is 14. If there are ten electrons in the anion, the number neutrons in the nucleus of atom X of the element will be –
(a) 10
(b) 14
(c) 7
(d) 5
Answer: (c) 7

Question. An isotone of \( ^{76}_{32}Ge \) is :
(a) \( ^{77}_{32}Ge \)
(b) \( ^{77}_{33}As \)
(c) \( ^{77}_{34}Se \)
(d) \( ^{79}_{34}Se \)
Answer: (a) \( ^{77}_{33}As \)
Isotones are elements which have some number of nuetrons.
\( ^{76}_{32}Ge \rightarrow 76 - 32 = 44 \)
\( ^{77}_{33}As \rightarrow 77 - 33 = 44 \)