Question:
Fill in the blanks:
Mass of 2 Hydrogen atoms is __________.
Atoms and Molecules
Q 1.
What is the chemical symbol for iron?
Q 2.
Define 'formula mass' of a compound.
Q 3.
(i) State the law of constant proportions.
(ii) Show that water illustrates the law of constant proportions.
Q 4.
What do we call those particles which have more or less electrons than the normal atoms ?
Q 5.
Explain with example that law of conservation of mass is valid for chemical reactions.
Q 6.
Which postulate of Dalton’s atomic theory can explain the law of definite proportions?
Q 7.
Fill in the blanks:
The atomic mass of sodium is 23. The gram atomic mass of sodium is _________.
Q 8.
Fill in the blanks:
One mole of water contains ______________ molecules.
Q 9.
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 10.
Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass?
Q 11.
What is the atomic mass unit?
Q 12.
Magnesium is two times heavier than C-12 atom, what shall be the mass of Mg atom in terms of atomic mass units? (Given mass of C-12 atom = 12u)
Q 13.
What is the molecular mass of a substance?
Q 14.
Define molecule. What are its important properties?
Q 15.
Fill in the blanks:
The chemical symbol of mercury is _________.
Q 16.
Name one element each which forms diatomic and tetra atomic molecule.
Q 17.
Name one element which forms diatomic and triatomic molecule.
Q 18.
What is gram-atomic mass of an element?
Q 19.
Fill in the blanks:
Atoms can be observed using ____________ Microscope.
Q 20.
What is gram-molecular mass of a substance?
Q 21.
Define mole. What is its significance?
Q 22.
Convert 12 g of oxygen gas into moles.
Q 23.
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 24.
What is the significance of a chemical symbol?
Q 25.
Fill in the blanks:
According to law of definite proportions, in a chemical substance the elements are always present in __________ proportions by mass.
Q 26.
Fill in the blanks:
The chemical symbol of flourine is ________.
Q 27.
Give one major drawback of Dalton's atomic theory of matter.
Q 28.
If 16 g of oxygen contains 1 mole of oxygen atoms, calculate the mass of one atom of oxygen.
Q 29.
How many atoms are there in 0.25 mole of hydrogen ?
Q 30.
What is the law of conservation of mass?
Q 31.
What are the postulates of Dalton's atomic theory?
Q 32.
What is relative atomic mass of an element? How it is related to atomic mass unit?
Q 33.
Give four examples of diatomic molecules.
Q 34.
Give the names of the elements present in the following compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.
Q 35.
Find out number of atoms in 15 moles of He.
Q 36.
Calculate the molecular masses of the following compounds :
(a) Hydrogen sulphide, H2S
(b) Carbon disulphide, CS
Q 37.
Who established the two important laws of chemical combinations?
Q 38.
Fill in the blanks:
The atomicity of sulphur S
8 is ________.
Q 39.
What are ionic compounds?
Q 40.
Which has more number of atoms, 100 grams of sodium or 100 grams of iron (given, atomic mass of Na = 23 u, Fe = 56 u)?
Q 41.
What is the mass of:
(a) 0.2 mole of oxygen atoms?
(b) 0.5 mole of water molecules?
Q 42.
Calculate the number of molecules of sulphur (S
8) present in 16 g of solid sulphur.
Q 43.
Calculate the number of molecules of phosphorus (P
4) present in 31 gram of phosphorus.
Q 44.
What is the mass of 5 moles of sodium carbonate (Na
) ?(Atomic masses : Na = 23 u ; C = 12 u ; O = 16 u)
Q 45.
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 46.
Fill in the blanks:
The mass of 1 mole of a substance is called its _____________.
Q 47.
Name the element having following Latin names
(i) Stibium
(ii) Cuprum
(iii) Argentum
(iv) Natrium
(v) Stannum
(vi) Wolfram
(vii) plumbum
(viii) Kalium
Q 48.
How will you define chemical symbol?
Q 49.
Can atoms of an element exist independently? Give examples of elements which exist in atomic form. Give examples of elements that do not exist in atomic form.
Q 50.
Based on type of substance, how molecules are classified?
