The Most Important Chemistry Mcqs which are used in every type of competitive examination is stated as under;-
1. One atom of sodium is _________________________.
b. NA moles
c. Positively charged
d. 1/NA moles
2. Bismark brown is a dye. Its molar mass is 228.3 g/mol. When the dye was analyzed by a scientist, it was found that it contains 30.68% nitrogen. How many nitrogen atoms are there in each Bismark brown molecule?
3. The mass of 2 moles of sodium hydroxide will be
c. 40 g
d. 80 g
4. Consider the following reaction
2Al(s) + 3 Cl2(g) 2AlCl
The following figure represents a mixture of Al(S). Consider that each symbol is representing one mole of the substance. Which of the reactants will be consumed earlier and how many moles of the product will be formed.
a. Al and 4 mol of AICl3
b. Cl2 and 4 mol of AICl3
c. Cl2 and 6 mol of AICl3
d. both reactants will be consumed at the same time and 4 mol of AICl3
5. 10 moles of H2O contains
a. 100 moles of bonds
b. 100 moles of electrons
c. 30 atoms
d. 20 moles of hydrogen bonds
6. Ozone (03) filters the cosmic rays of sunlight. How many oxygen atoms are there in 0.2 mole of Ozone (03, molar mass 48.0 g/mol)?
a. 6.02 x 1022
b. 6.02 x 1023
c. 3.61 x 1023
d. 6 x 1023
7. On heating, the hydrated salt CaS04.xH20 loses its water of crystallization. In an experiment, it was found that when 0.2 mol of the hydrated salt was heated 0.10 mol of water was lost. What is the molecular formula of the hydrated compound?
8. Zirconium chloride reacts with magnesium to produce Zirconium.
ZrC14 + 2Mg 7-r + 2MgC12
How many moles of Zr would be produced if 0.2 mol of Mg metal is used in the reaction?
9. Tobacco contains a poisonous alkaloid called Nicotine. The molecular formula of nicotine is CloH14N2 (molar mass = 162.23 g). The mass percentage of nitrogen in nicotine, is?
10. A sample of an ionic compound contains 2.82 g Na, 4.35 g Cl, and 7.83 g O. The empirical formula of this compound is:
11. How many carbonate ions are there in 50g of CaC03?
a. 50/100 x 6.022 x 1023
b. 100/50 x 6.022 x 1023
c. 50 x 6.022 x 1023
d. 50 x100 / 6.022 x 1023
12. Stoichiometric calculations can only be carried out when
a. The reaction is irreversible
b. There is no side reaction
c. At least one of the reactants is consumed completely
d. All of the above
13. How many molecules of oxygen will be produced from the decomposition of 2 kilomoles of potassium chlorate according to the following reaction?
2KClO 3(s) _______ 2KCL(s) +302(g)
a. 3 x 6.022 x 1023
c. 3 x 103 x 6.022 x 1023
d. 3 x 103 x 6
14. Which of the following represents 1 mol of the substances?
a. 4g helium
b. 6,022 x1024 molecules of NH3
c. 40g calcium chloride
d. 6.022 molecules of
15. Urea (NH2)2CO is used as fertilizer. If 2 moles of urea is present in a container than a mass of the nitrogen in the compound will be
16. 8g of methane (CH4) contains
a. 4 hydrogen atoms
b. 0.5 mol of carbon atoms
c. carbon atoms
d. hydrogen atoms
17. A beaker has 180g of water in it. Number c moles of oxygen atoms in it will be
18. 23.5g of N2 contain as many atoms as in
a. 23.5g ofO2
b. 23.5g of CO
c. 23.5g of H2
d. 23.5g of CL2
19. Sample containing a maximum number of atoms among the following is
a. 6g of He
b. 28g of N2
c. 4g of H2
d. 48g of O2
20. If a piece of 4 mol of lithium is dropped in 72g of water in a container then
a. 2 mol of lithium is left unreacted
b. 2 mol of water is left unreacted
c. 2.5 mol of lithium is left unreacted
d. None of the reactants is left unreacted
21. If sulfur is in excess then production of 2 mol of ferrous sulfide requires
a. 2g of iron
b. 4g of iron
c. 56g of iron
d. 112g of iron
22. DDT is widely used as an insecticide. Its molar mass is 354.5g/mol. When DDT was analyzed by a chemist he found that it contains 47.4% carbon. How many carbon atoms are there in each DDT molecule?
23. One gram atom of chlorine is equal to
a. One mole of chlorine atoms
c. One gram of chlorine atoms
d. a, b both are correct
24. All of the following are not quantitative statements except
a. This ore contains copper.
b. That E.D.T.A solution is 0.1 molar.
c. Let’s start with an aqueous solution first.
d. It is sour it must be the citric acid.
25. If theoretical and percentage yields of a product are 50g and 90g respectively, then actual yield of the product will be
26. How many liters of sulfur dioxide at STP is produced from burning 1.6g of sulfur in excess of oxygen? S +0 2(g) —9 SO2(g)
27. Which one among the following is NOT correct for a mole?
a. it is a counting unit
b. it is the gram atomic or gram formula mass of a substance
c. it contains particles
d. it contains a different number of particles for different substances
28. How much calcium is present in 0.1g of CaC03?