### Stoichiometry

1. The following element(s) undergo disproportionation in the alkaline medium
1) P           2) S        3) Cl        4) all the above
Ans: (4)
Explanation: P, S, Cl undergo disproportionation reactions as all will have 3 different oxidation states.

2. Consider the following statements for the reaction
KIO3 + 5 KI + 6 HC 3 I2 + 6 KCl + 3 H2O
1) I - is reduced to I2
2) IO3- is oxidised to I2
3) Oxidation number of I increases from -1 (KI) to zero (in I2)
4) Oxidation number of Cl increases from -1 (HCl) to +1 (in KCl)
Ans: (3)
Explanation: Oxidation state of I in KI = -1, in I2 = 0.

3. The values of x, y, z in the following reaction are, respectively

1) 2, 5, 8       2) 2, 5, 16        3) 5, 2, 8         4) 5, 2, 16
Ans: (2)

4. The oxidation state of Cr in [Cr(NH)3)4Cl2]+ is
1) +3         2) +2          3) +1         4) +6
Ans: (1)
Explanation: The oxidation state of Cr = x + 4(0) + 2(-1) = +1
∴ x = 1 + 2 = +3

5. The oxidation state of Cr in the final product formed by the reaction between KI and acidified KMnO4 is
1) +6        2) +2        3) +3          4) +4
Ans: (3)
Explanation: Cr2O7-2 + 14 H+ + 6 I 2 Cr+3 + 7 H2O + 3 I2

6. An organic compound having molecular mass 60 is found to contain C = 20%, H = 6.67% and N = 46.67% while rest is Oxygen. On heating it gives NH3 along with a solid residue. This residue gives violet colour with alkaline copper sulphate solution. The compound is
1) CH3NCO      2) (NH2)2CO      3) CH3CONH2     4) CH3CH2CONH2
Ans: (2)

7. Vapour density is

Ans: (3)

8. Among the following pairs of compounds, the one that illustrates the law of multiple proportions is
1) CuO and Cu2O           2) H2S and SO2

3) NH3 and NCl3        4) CS2 and FeSO4
Ans: (1)

9. 3 g of an oxide of a metal is converted to chloride completely and it yielded 5 g of chloride. The equivalent weight of the metal is
1) 20      2) 12         3) 3.325          4) 33.25
Ans: (4)

10. Maximum number of molecules are present among the following is
1) 100 cc of CO2 at STP       2) 200 cc of NH3 at STP
3) 50 cc of SO2 at STP         4) 150 cc of N2 at STP
Ans: (2)
Explanation: Volume at STP  no. of molecules.
NH3 has larger volume, so maximum no. of molecules are present in it.

11. If the true value for a result is 3 g and a student takes 4 measurements and reports the results as 2.94, 2.97, 2.99 and 3.01 g. Where the values 3.01 g and 2.99 g are respectively
1) both are not accurate                            2) both are not precise
3) both are accurate                                  4) both are precise and accurate
Ans: (4)
Explanation: As both the values are very close with 3 g, they are precise and accurate.

12. Incorrect statement among the following is
1) all non-zero digits are significant.
2) Zeros preceding to first non-zero digit are significant.
3) Zeros between two non-zero digits are significant.
4) 0.200 g has 3 significant figures.
Ans: (2)
Explanation: All zeros preceding to first non-zero digits are not significant.

13. Equivalent weight of Permanganate ion in acid medium is
1) 23.78                    2) 31.6                          3) 158                         4) 119
Ans: (1)

14. Molality of 3 M solution of NaCl having density 1.25 g/ lit is
1) 3.79 m                     2) 2.79 m                     3) 1.79 m                       4) 3 m
Ans: (2)

15. Formation of Ozone hole is an example of
1) Oxidation phenomenon          2) Reduction phenomenon
3) Redox phenomenon              4) None of the above
Ans: (3)
Explanation: Conceptual

16. Oxidation number of gold in the compound HAuCl4 is
1) +1                           2) +2                            3) 0                             4) +3
Ans: (4)
Explanation: HAuCl4 = + 1 + x - 4 = 0 ∴  x = +3

17. Disproportionation reaction is not shown by the ion among ClO-, ClO2-, ClO3- and ClO4- is
1) ClO4-       2) ClO3-      3) ClO2-        4) ClO-
Ans: (1)
Explanation: Oxidation state of Cl in ClO4- is +7 (highest). It can undergo only reduction but not oxidation.

18. Individual oxidation states of carbon atoms present in C3O2 are

Ans: (3)

19. The volume of H2 gas at 273 K and 1 atm pressure will be consumed in obtaining 21.6 g of elemental Boron (atomic mass = 10.8) from the reduction of BCl3 is
1) 44.8 L       2) 67.2 L         3) 22.4 L       4) 89.6 L
Ans: (2)
Explanation:   2 BCl3        +          3 H2                          2 B        +         6 HCl
3 × 22.4 = 67.2 L                2 × 10.8 = 21.6 g.

20. A gaseous mixture contains 50% Helium and 50% Methane by volume. The percent by weight of Methane in the mixture is
1) 20%        2) 50%         3) 75%        4) 80%
Ans: (4)

21. The equivalent weight of phosphoric acid in the reaction
NaOH + H3PO NaH2PO4 + H2O is
1) 49           2) 98         3) 24.5          4) 16.5
Ans: (2)

22. The volumes of H2 gas and Cl2 gas are required at S.T.P. conditions for the formation of 3.65 g of HCl are
1) 1.12 L, 1.12 L     2) 1.12 L, 2.24 L     3) 1 L, 1 L        4) 2.24 L, 1.12 L
Ans: (1)

23. An element X has x200 - 90%, x199 - 8%, x202 - 2%. Average atomic mass of the element X is
1) 199 amu         2) 209 amu        3) 206 amu         4) 200 amu
Ans: (3)

24. 80 g of Oxygen contains as many as atoms as in
1) 40 g of Hydrogen           2) 10 g of Hydrogen
3) 1 g of Hydrogen            4) 5 g of Hydrogen
Ans: (4)

25. How many moles of Mg3(PO4)2 will contain 0.25 moles of Oxygen atoms?
1) 6.15 × 10-3   2) 1.25 × 10-2     3) 3.125 × 10-2       4) 2.5 × 10-2
Ans: (3)

Posted Date : 15-10-2020