Question:
Calculate the molecular mass of chloroform (CHC1
Atoms and Molecules
Q 1.
What is gram-atomic mass of an element?
Q 2.
Fill in the blanks:
According to law of definite proportions, in a chemical substance the elements are always present in __________ proportions by mass.
Q 3.
Fill in the blanks:
The atomic mass of sodium is 23. The gram atomic mass of sodium is _________.
Q 4.
How many atoms are there in 0.25 mole of hydrogen ?
Q 5.
Define 'formula mass' of a compound.
Q 6.
What is the mass of 5 moles of sodium carbonate (Na
) ?(Atomic masses : Na = 23 u ; C = 12 u ; O = 16 u)
Q 7.
Write the formulae of the following compounds. Also name the elements present in them.
(a) Water
(b) Ammonia
(c) Methane
(d) Sulphur dioxide
(f) Ethanol
Q 8.
Which of the following statements is NOT true about an atom?
(a) Atoms are the building blocks from which molecules and ions are formed.
(b) Atoms cannot exist independently.
(c) Atoms are neutral in nature
(d) Atoms combine together to form matter that we can see, feel or touch.
Q 9.
What is the chemical symbol for iron?
Q 10.
Write the chemical symbols of the following:
(i) Gold
(ii) Iron
(iii) Chlorine
(iv) Mercury
Q 11.
Name one element each which forms diatomic and tetra atomic molecule.
Q 12.
Name the international organization who approves names of elements.
Q 13.
If one mole of carbon atoms weighs 12 gram, what is the mass (in gram) of 1 atom of carbon?
Q 14.
Who established the two important laws of chemical combinations?
Q 15.
Who proposed Law of Definite Proportions (or Law of Constant Composition)?
Q 16.
State Law of constant proportions. Explain with an example.
Q 17.
Define molecule. What are its important properties?
Q 18.
Fill in the blanks:
The chemical symbol of flourine is ________.
Q 19.
Hydrogen and oxygen combine in the ratio of 1:8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?
Q 20.
What are the postulates of Dalton's atomic theory?
Q 21.
Fill in the blanks:
The mass of 5 moles of ammonia (NH
3) is __________.
Q 22.
Give four examples of diatomic molecules.
Q 23.
What is the significance of a chemical symbol?
Q 25.
What are polyatomic ions? Give examples?
Q 26.
Give the names of the elements present in the following compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.
Q 27.
How many atoms are present in a
(i) H
2S molecule and
(ii) PO
43- ion?
Q 28.
What is the law of conservation of mass?
Q 29.
Name the element having following Latin names
(i) Stibium
(ii) Cuprum
(iii) Argentum
(iv) Natrium
(v) Stannum
(vi) Wolfram
(vii) plumbum
(viii) Kalium
Q 30.
Which element has the smallest atom in size?
Q 31.
Fill in the blanks:
The chemical symbol of mercury is _________.
Q 32.
Write down the names of compounds represented by the following formulae:
(i) Al
2(SO
4)
3 (ii) CaCl
2 (iii) K
2SO
4 (iv) KNO
3 (v) CaCO
3
Q 33.
Give one major drawback of Dalton's atomic theory of matter.
Q 34.
Dalton's atomic theory says that atoms are indivisible. Is this statement still valid ? Give reasons for answer.
Q 35.
Fill in the blanks:
Atoms can be observed using ____________ Microscope.
Q 36.
Fill in the blanks:
One mole of water contains ______________ molecules.
Q 37.
What are ionic compounds?
Q 38.
Name one element which forms diatomic and triatomic molecule.
Q 39.
Who introduced the term 'mole' in chemistry?
Q 40.
What is the mass of
(a) 1 mole of nitrogen atoms?
(b) 4 moles of aluminium atoms (Atomic mass of aluminium = 27)?
(c) 10 moles of sodium sulphite (Na
2SO
3)?
Q 41.
Calculate the molecular mass of nitric acid,HNO
Q 42.
Name the elements water is made of. What are the valencies of these elements ? Work out the chemical formula for water.
Q 43.
How many moles are there in 34.5 g of sodium ? (Atomic mass of Na = 23 u)
Q 44.
When 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.00 g of carbon is burnt in 50.00 g of oxygen? Which law of chemical combination will govern your answer?
Q 45.
Which postulate of Dalton’s atomic theory can explain the law of definite proportions?
Q 46.
Fill in the blanks:
___________ is the combining capacity of an element.
Q 47.
Fill in the blanks:
Atomic radius is measured in __________.
Q 48.
Fill in the blanks:
Mass of 2 Hydrogen atoms is __________.
Q 49.
What is relative atomic mass of an element? How it is related to atomic mass unit?
Q 50.
Fill in the blanks:
An element has only one type of __________.
