Question:
'If 100 grams of calcium carbonate (whether in the form of marble or chalk) are decomposed completely,then 56 grams of calcium oxide and 44 grams of carbon dioxide are obtained'.Which law of chemical combination is illustrated by this statement ?
Answer:
Law of conserv ation of mass
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.
What is the chemical symbol for iron?
Q 6.
Define 'formula mass' of a compound.
Q 7.
What is the mass of 5 moles of sodium carbonate (Na
) ?(Atomic masses : Na = 23 u ; C = 12 u ; O = 16 u)
Q 8.
Who established the two important laws of chemical combinations?
Q 9.
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 10.
Write the chemical symbols of the following:
(i) Gold
(ii) Iron
(iii) Chlorine
(iv) Mercury
Q 11.
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 12.
Who proposed Law of Definite Proportions (or Law of Constant Composition)?
Q 13.
Name the international organization who approves names of elements.
Q 14.
Define molecule. What are its important properties?
Q 15.
Name one element each which forms diatomic and tetra atomic molecule.
Q 16.
If one mole of carbon atoms weighs 12 gram, what is the mass (in gram) of 1 atom of carbon?
Q 17.
What are the postulates of Dalton's atomic theory?
Q 18.
What is the significance of a chemical symbol?
Q 19.
Fill in the blanks:
The chemical symbol of flourine is ________.
Q 20.
Give four examples of diatomic molecules.
Q 22.
State Law of constant proportions. Explain with an example.
Q 23.
Fill in the blanks:
The chemical symbol of mercury is _________.
Q 24.
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 25.
Which postulate of Dalton’s atomic theory can explain the law of definite proportions?
Q 26.
Fill in the blanks:
Atomic radius is measured in __________.
Q 27.
Fill in the blanks:
Atoms can be observed using ____________ Microscope.
Q 28.
What is relative atomic mass of an element? How it is related to atomic mass unit?
Q 29.
What are polyatomic ions? Give examples?
Q 30.
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 31.
What are ionic compounds?
Q 32.
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 33.
Name the element having following Latin names
(i) Stibium
(ii) Cuprum
(iii) Argentum
(iv) Natrium
(v) Stannum
(vi) Wolfram
(vii) plumbum
(viii) Kalium
Q 34.
Which element has the smallest atom in size?
Q 35.
Give examples of triatomic molecules.
Q 36.
Give the names of the elements present in the following compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.
Q 37.
How many atoms are present in a
(i) H
2S molecule and
(ii) PO
43- ion?
Q 38.
Give one major drawback of Dalton's atomic theory of matter.
Q 39.
Calculate the molecular mass of ethanoic acid, CH
Q 40.
Calculate the molecular mass of chloroform (CHC1
Q 41.
Explain with example that law of conservation of mass is valid for chemical reactions.
Q 42.
Fill in the blanks:
The mass of 5 moles of ammonia (NH
3) is __________.
Q 43.
What is the atomic mass unit?
Q 44.
Fill in the blanks:
One mole of water contains ______________ molecules.
Q 45.
Name one element which forms diatomic and triatomic molecule.
Q 46.
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 47.
Calculate the number of aluminium ions present in 0.051 g of aluminium oxide.
(
Hint: The mass of an ion is the same as that of an atom of the same element. Atomic mass of Al = 27 u)
Q 48.
What are the building blocks of matter ?
Q 49.
Name the unit in which the radius of an atom is usually expressed.
Q 50.
Dalton's atomic theory says that atoms are indivisible. Is this statement still valid ? Give reasons for answer.
