Online Test of Chapter 3 Atoms and Molecules 3 Science| Class 9th Science
Questions :
1. The percentage of water of crystallisation in CuSO4.5H2O is
(a) 36.07
(b) 72.14
(c) 9.02
(d) 56.15
2. Which has the maximum number of atoms?
(a) 108 g of Ag
(b) 56 g of Fe
(c) 27 g of Al
(d) 24 g of 12C
3. 8 g of O2 has the same number of molecules as
(a) 22 g of CO2
(b) 7 g of CO
(c) 14 g of CO
(d) 28 g of CO
4. A sample of pure water, irrespective of source, contains 88.89% oxygen and 11.11% hydrogen by mass. The data supports the
(a) Law of conservation of mass
(b) Law of constant composition
(c) Law of multiple proportions
(d) None of these
5. 10 g of CaCO3 on heating gave 4.4 g of CO2 and 5.6 g of CaO. The observation is in agreement with the
(a) Law of constant composition
(b) Law of conservation of mass
(c) Law of definite proportion
(d) Law of multiple proportion.
6. The atomic mass of potassium is 39. The number of moles in 78 g of potassium is
(a) 78
(b) 39
(c) 2
(d) 1
7. The mass of sodium in 11.7 g of sodium chloride is
(a) 2.3 g
(b) 4.6 g
(c) 6.9 g
(d) 7.1 g
8. The correct formula of aluminium sulphate is
(a) Al2SO4
(b) AlSO4
(c) Al2(SO4)3
(d) Al3(SO4)2
9. The formula unit mass of Na2SO4.10H2O is
(a) 142 u
(b) 322 u
(c) 286 u
(d) 23 u
10. An element A is tetravalent and element B is divalent. The formula of the compound formed by these two elements is
(a) AB2
(b) A2B
(c) A2B4
(d) AB
Chapter 3 Atoms and Molecules Quiz 3| Class 9th
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Question 1 of 10
1. Question
The percentage of water of crystallisation in CuSO4.5H2O is
Correct
Total mass of CuSO4.5H2O = (63.5 + 32 + 64) + (5×18) = 159.5 + 90 = 249.5
Percentage of water of crystallization = (90/249.5) x 100 = 36.07Incorrect
Total mass of CuSO4.5H2O = (63.5 + 32 + 64) + (5×18) = 159.5 + 90 = 249.5
Percentage of water of crystallization = (90/249.5) x 100 = 36.07 -
Question 2 of 10
2. Question
Which has the maximum number of atoms?
Correct
To calculate no. of atoms, first calculate the mass of 1 atom. After that, divide the given mass by mass of 1 atom.
For example, Mass of 1 atom of O = 16 g
Therefore, No. of atoms in 32 g of O = 36/18 = 2Incorrect
To calculate no. of atoms, first calculate the mass of 1 atom. After that, divide the given mass by mass of 1 atom.
For example, Mass of 1 atom of O = 16 g
Therefore, No. of atoms in 32 g of O = 36/18 = 2 -
Question 3 of 10
3. Question
8 g of O2 has the same number of molecules as
Correct
Mass of O2 = 32g
No. of molecules in 8g of O2 = 32/8 = ¼
Mass of CO = 28g
No. of molecules in 7g of CO = 7/28 = 1/4Incorrect
Mass of O2 = 32g
No. of molecules in 8g of O2 = 32/8 = ¼
Mass of CO = 28g
No. of molecules in 7g of CO = 7/28 = 1/4 -
Question 4 of 10
4. Question
A sample of pure water, irrespective of source, contains 88.89% oxygen and 11.11% hydrogen by mass. The data supports the
Correct
Incorrect
-
Question 5 of 10
5. Question
10 g of CaCO3 on heating gave 4.4 g of CO2 and 5.6 g of CaO. The observation is in agreement with the
Correct
Incorrect
-
Question 6 of 10
6. Question
The atomic mass of potassium is 39. The number of moles in 78 g of potassium is
Correct
Mass of 1 mole of potassium = 39 g
78 g of potassium = 78/39 = 2 moleIncorrect
Mass of 1 mole of potassium = 39 g
78 g of potassium = 78/39 = 2 mole -
Question 7 of 10
7. Question
The mass of sodium in 11.7 g of sodium chloride is
Correct
Mass of NaCl = 23 + 35.5 = 58.5 g = 1 mole of NaCl
11.7 g of NaCl = 11.7/58.5 = 0.2 mole
0.2 mole of Na = 0.2 x 23 = 4.6 g of NaIncorrect
Mass of NaCl = 23 + 35.5 = 58.5 g = 1 mole of NaCl
11.7 g of NaCl = 11.7/58.5 = 0.2 mole
0.2 mole of Na = 0.2 x 23 = 4.6 g of Na -
Question 8 of 10
8. Question
The correct formula of aluminium sulphate is
Correct
Valence of Al = 3+
Valence of SO4 = 2-
Formula of aluminium sulphate = Al2(SO4)3Incorrect
Valence of Al = 3+
Valence of SO4 = 2-
Formula of aluminium sulphate = Al2(SO4)3 -
Question 9 of 10
9. Question
The formula unit mass of Na2SO4.10H2O is
Correct
(46 + 32 + 64) + (10 x 18) = 142 + 180 = 322 u
Incorrect
(46 + 32 + 64) + (10 x 18) = 142 + 180 = 322 u
-
Question 10 of 10
10. Question
An element A is tetravalent and element B is divalent. The formula of the compound formed by these two elements is
Correct
Incorrect