CBSE Important Questions(Long questions) for Atoms and Molecules

Given below are the CBSE Important Questions(Long questions) for Atoms and Molecules
(a) Concepts questions
(b) Calculation problems
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Question 1.
Mention the difference between 2N and N2?
Question 2.
Nitrogen and Hydrogen combine in the ratio 14:3 by mass to form ammonia molecule. Find the formulae of ammonia molecule by calculating the molar ratio?
Question 3.
An element ‘Y’ forms an oxide whose chemical formulae is Y2O3
a)State the valency of Y.
b)Write the chemical formulae of its: (a) Sulphate and (b) Chloride?
Question 4.
Define mole? Calculate the number of moles in 22g of carbon dioxide?
Question 5.
State three rules for writing the chemical formulae.
Question 6.
Write the chemical formulae for the chloride of magnesium?
Question 7.
Write down the chemical formulae of:
(a)Magnesium nitride
(b)Calcium nitrate
(c)Sodium nitrite
Question 8.
Find the number of atoms present in:
(a)SO2 molecule
(b)SO4 ion
Question 9.
If one mole of carbon atoms weighs 12 g, what is the mass of 1 atom of carbon?
Question 10.
Derive the formula of the compound formed between Na+ and SO4-2
Question 11.
Write the chemical formulae for the compounds formed by the calcium ion with phosphate, sulphate and hydrogen carbonate ions?
Question 12.
Write the ratio by mass of Hydrogen and oxygen in one molecule of water?

Question 13.
State the number of hydrogen atoms in 1 g of hydrogen?
Question 14.
The relative atomic mass of oxygen atom is 16. Explain its meaning?
Question 15.
Calculate the number of molecules of SO2 present in 44 g of it?
Question 16.
If one molecule of oxygen atoms weighs 16 g, find the mass of one atom of oxygen?
Question 17.
Sodium is represented as $^{23}_{11}Na$
(a)What is its atomic mass?
(b)Write its gram atomic mass?
(c)How many atoms of Na will be there in 11.5 g of the sample?
Question 18.
Calculate the molar mass of the following compounds and identify the poly-atomic ions present in each of them:
(a)MgSO4
(b)Na2CO3
Question 19.
Define formulae unit mass of compounds. Calculate the formulae unit mass of :
(a)Na2CO3.10H2O
(b)CuSO4
Question 20.
The atomic mass of calcium is 40 u. What will be the number of calcium atoms in 0.4 of calcium?
Question 21.
Molar mass of nitrogen is 14 u. What will be the mass of one atom of nitrogen?
Question 22.
How many atoms are present in:
(a)MnO2 molecule
(b)CO molecule
Question 23.
Calculate the number of aluminium ions present in 0.051 g of aluminium oxide?
Question 24.
Calculate the number of molecules of sulphur (S-8) present in 8g of solid sulphur?
Question 25.
Calculate the number of molecules in 4g of methane?
Question 26.
Write down the names of compounds represented by the following chemical formulae:
(a)AI2 (SO4)3
(b)CaCl2
(c)NaNO3
Question 27.
Compare relative molar mass and relative formula unit mass?
Question 28.
What is the mass of:
(a)1 mole of nitrogen atoms?
(b)4 mole of aluminium atoms?
(c)10 mole of sodium sulphite (Na2SO3)
(d) 0.2 mole of water
Question 29.
Calculate the molar mass of HNO3. Compare it with its formula unit mass?
Question 30.
A 0.48g sample of compounds of oxygen and boron was formed by analysis to contain 0.192 g of boron and 0.2888g of oxygen. Calculate the percentage composition of the compound by weight?

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