-MCQ,s of chemistry- mole concept chapter-01.

     Here we explain top class of mcqs chemistry first year that asked in past competitive examination with proper explanation of answer key....                                

                         Top-10-MCQ,s of Chemistry

1. Which one of the following contain maximum number of atoms?
A)  6-mole of sulphur.

B)  2.0-mole of S₈

C)   5.0-mole of SO₂

D)  44.8dm³of CO₂ at STP.

2.The number of atoms in 18g of H₂0 are equal to:

A)  6.02 x 10 ²³ atoms.

B)  6.02 x 10 ²⁴ atoms.

C) 1.806 x 10 ²⁴ atoms.

D)  3.052 x 10 ²³ atoms.

3.Theoretical yield is always--------.

A) Less than practical yield.

B)Greater than actual yield.

C) Both are equal.

D)None of above.

4.How many grams of Al₂O₃ will be obtained if 13.5 g of aluminium completely react with oxygen as.
       4Al +4O₂--------> 2Al₂O_3.  (Molar mass of Al=27g/mole.).
A)  25.5 g.

B) 27.54 g.

C) 54.27 g.

D)14.27 g.

5.What is the number of hydrogen atoms in 5-mole of water?

A)  3.0115 x 10 ²⁴ atoms.

B)  6.02 x 10 ²⁴ atoms.

C) 6.02 x 10 ²³ atoms.

D) 5.02 x 10 ²³ atoms.

6.2KClO3 ---> 2KCl +3O₂, how many moles of KClO₃ are required to       prepare 6 moles of oxygen?      

A) 3.17 mol.

B) 5.01 mol.

C)  4.0 mol.

D) 2.0 mol.

7.Which one of the following contains the greatest number of atoms?

A)  4g of hydrogen.

B) 4g of magnesium.

C) 71g of chlorine.

D)127g of iodine.

8.Calculate the number of moles of NaCl in 75g of table salt?
A)  0.643.

B) 0.799.

C)  28.0.

D) 1.28.

9.The number of oxygen atoms in 0.5 mole of Al₂ (CO₃)₃ is-------

A) 4.5 x 10 ²³.

B) 3.6 x 10 ²⁴.

C) 2.7 x 10 ²⁴.

D) 9.0 x 10 ²³.

10.10L of Cl2 gas reacts with 40L of H2 gas under same condition of    temperature and pressure. How much volume of HCl should be produced?
A).40L.

B).30L.

C).20L.

D).10L

ANSWER KEY WITH EXPLANATION.

1	B	As by formula: No of atom = mole x number of given atom x NA.
2	C	The total number of atoms in a molecule can be find out by formula:  moles X number of atoms X NA
3	B	Based on general data.
4	A	According to reaction 108g of Al react with excess oxygen to produce 204 g of Al2O3, then 13.5 gram of Al will be producing 25.5 gram of Al2O3.
5	B	As by formula= mole X number of H-atom X NA
6	C	According to reaction 2-mole of KClO3 provide 3-mole of oxygen, then 6 moles of oxygen will be producing by breakdown of 4 mole of KClO3.
7	A	As by formula: No of atom = mole x number of given atom x NA.
8	D	As by formula of mole:  mole= given mass/molar mass.
9	A	As number of atoms in a molecule=mole X no. of given atom x NA.
10	C	Cl2 is limiting reagent. Only 10L of H2 will react. According to the reaction above, when one mole of each gas reacts, 2 moles of HCl are produced.  So, the volume that will be produced in this case will be 10×2=20l.