# Extra Questions with answers for Atoms and Molecules

Given below are the Extra questions with answers for Atoms and Molecules of Class 9 Science. These are important questions for examination also
(a) 1 Mark Questions
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## 1 Marks Questions

Question 1.
Each Part Carry 1 Marks
(i) Name the body which approves the nomenclature of elements and compounds.
(ii) The symbol of sodium is written as Na and not as S. Give reason.
(iii) Name one element which form diatomic and one which form tetra atomic molecules.

Question 2.
Each Part Carry 1 Marks
Write down the name of the following compounds:
(a)KNO3
(b)CaCO3
(c)Ca(HCO3)2
(d)AI2 (SO4)3
(e)CaCl2
(f)NaNO3

Question 3.
Each Part Carry 1 Marks
write the symbol and Latin name of the following elements:
(a)sodium
(b)Potassium
Question 4.
Each Part Carry 1 Marks
Write atomicity of the following:
(a)Sulphur
(b)Phosphorus
(c)Oxygen
(d) Sodium (e)Argon
(f) Neon

Question 5.
Each Part Carry 1 Marks
Find the number of atoms present in:
(a)SO2 molecule
(b)SO4 ion

Question 6
Each Part Carry 1 Marks
Write formulas for ionic compounds formed from:
(a) Na and F
(b) Na and O,
(c) Mg and F
(d) AI and C
Question 7
Each Part Carry 1 Marks
Write the chemical formulas for the following compounds:
(a) Copper (I) oxide
(b) Potassium peroxide
(c) Mercury (I) bromide
(d) Iron (III) carbonate
(e) Sodium hydrobromite.

Question 8
Each Part Carry 1 Marks
Give the name for each of the following acids:
(a) HBrO3,
(b) HBr,
(c) H3PO4,
(d) HCIO
(e) HIO3

Question 1.
What is meant by the term chemical formula?
Question 2.
Name two scientists who established the laws of chemical combination?
Question 3.
What is meant by a molecule? Give examples?
Question 4.
Name the international organization which approves the names given to the elements?

Question 5.
What is the difference between an atom and a molecule?
Question 6.
Define polyatomic ion?
Question 7.
Write the chemical formulae for the chloride of magnesium?
Question 8.
Define atomicity?
Question 9.
Mention the difference between 2N and N2?

Question 10.
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 11
What is molecular weight? Explain with example.

Question 1.
When 3.0g of magnesium is burnt in 2.00g of oxygen, 5.00g of magnesium oxide is produced. What mass of magnesium oxide will be formed when 3.00g magnesium is burnt in 5.00g of oxygen? Which law of chemical combination will govern your answer?
Question 2.
‘Atoms of most elements are not able to exist independently’. Name two atoms which exist as independent atoms?
Question 3.
Define atomic mass unit? State how do atoms exist?
Question 4.
The atomic number of three elements A, B, and C are 9, 10, and 13 respectively. Which of them will form a cation?
Question 5.
How would you differentiate between a molecule of element and a molecule of compound? Write one example of each type?
Question 6.
Provide a difference between cations and anions, along with an example for each.

Question 7.
State the postulates of Dalton’s atomic theory which indicates the law of constant proportions?
Question 8.
Calculate the number of molecules in 4g of methane?
Question 9.
What formed the basis for John Dalton to formulate Dalton’s atomic theory?
Question 10.
State the law of conservation of mass. Is this law applicable to the chemical reactions? Elaborate your answer with the help of an example?
Question 11.
Compare relative molar mass and relative formula unit mass?
Question 12.
Calculate the molar mass of HNO3. Compare it with its formula unit mass?

Question 1.
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 2.
Calculate the molar mass of the following compounds and identify the poly-atomic ions present in each of them:
(a)MgSO4
(b)Na2CO3

Question 3.
Define formulae unit mass of compounds. Calculate the formulae unit mass of :
(a)Na2CO3.10H2O
(b)CuSO4
Question 4.
How many atoms are present in:
(a)MnO2 molecule
(b)CO molecule

Question 5.
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 6.
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?
Question 7.
State two examples in each case and write their chemical formulae:
(a)Molecules having one kind of atoms only.
(b)Molecules having two different kinds of atoms.
(c)Molecules having three different kinds of atoms.
Question 8.
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 9
(i) Distinguish between an atom and a molecule.
(ii) Differentiate between atom and ion.