Question:
What are the postulates of Dalton's atomic theory?
Answer:
Dalton's theory states that matter, whether an element, a compound or a mixture is composed of small particles called atoms.
The postulates are:
- All matter is made of very tiny particles called atoms.
- Atoms are indivisible particles i.e. can neither be created or destroyed in a chemical reaction. (Law of Conservation of mass)
- Atoms of a give element have same mass and identical chemical properties.
- Atoms of different elements have different masses and chemical properties.
- Atoms combine in the ratio of small whole numbers to form compounds. A chemical reaction is a re-arrangement of atoms. (Law of Multiple Proportions)
- The relative number and kinds of atoms are constant in a given compound. (Law of Definite Proportions)
Atoms and Molecules
Q 1.
What is the mass of:
(a) 0.2 mole of oxygen atoms?
(b) 0.5 mole of water molecules?
Q 2.
Write the full form of IUPAC.
Q 3.
What name is given to the number 6.022 x 10
Q 4.
How many moles are 3.6 g of water ?
Q 5.
If one mole of nitrogen molecules weighs 28 g, calculate mass of one molecule of nitrogen in grams.
Q 6.
An element Z has a valency of 3. What is the formula of oxide of Z ?
Q 7.
What is the difference between a cation and an anion ? Explain with examples. Using this information, write down the formulae of:
(i) Sodium sulphide
(ii) Copper nitrate
Q 8.
How many moles of calcium carbonate (CaCO
Q 9.
What is the numerical value of Avogadro number ?
Q 10.
Is there any exception to law of conservation of mass?
Q 11.
What is meant by atomicity ? Explain with two
Q 12.
The molecular formula of glucose is C
Q 13.
What do we call those particles which are formed :
(a)by the gain of electrons by atoms ?
(b)by the loss of electrons by atoms ?
Q 14.
What is an ion ? How is an ion formed ? Explain with the help of two examples of different ions.
Q 15.
What is the mass of 0.2 mole of oxygen atoms ?
Q 16.
What is relative atomic mass of an element? How it is related to atomic mass unit?
Q 17.
How many moles are there in 4.6 gms of Sodium(Na)?
Q 18.
Calculate the molecular mass of chloroform (CHC1
Q 19.
How many moles are there in 34.5 g of sodium ? (Atomic mass of Na = 23 u)
Q 20.
Calculate the number of molecules in 4 g of oxygen.
Q 21.
(a) Define gram atomic mass of a substance.How much is the gram atomic mass of oxygen ?
(b) How many moles of oxygen atoms are present in one mole of the following compounds ?
(i)Al
(ii) co
2(iii) C1
(iv) H
(p)A1
Q 22.
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 23.
Fill in the blanks:
The _______________ of a compound is a symbolic representation of its composition.
Q 24.
Name the following compounds. Also write the symbols/formulae of the ions present in them :
(a) CuSO
Q 25.
If 16 g of oxygen contains 1 mole of oxygen atoms, calculate the mass of one atom of oxygen.
Q 26.
Show by means of calculations that 5 moles of CO, and 5 moles of H
do not have the same mass. How much is the difference in their masses ?
Q 27.
Fill in the blanks:
Atoms can be observed using ____________ Microscope.
Q 28.
Fill in the blanks:
The chemical symbol of mercury is _________.
Q 29.
Fill in the blanks:
Hydrogen and oxygen combines to form H
2O and H
2O
2. These two compounds obey the law of ____________________.
Q 30.
Dalton's atomic theory says that atoms are indivisible. Is this statement still valid ? Give reasons for answer.
Q 31.
Name the elements water is made of. What are the valencies of these elements ? Work out the chemical formula for water.
Q 32.
An element X has a valency of 4 whereas another element Y has a valency of 1. What will be the formula of the compound formed between X and Y ?
Q 33.
Find the mass of 2 moles of nitrogen atoms.
Q 34.
Calculate the mass in grams of 0.17 mole of hydrogen sulphide, H
Q 35.
If 12 g of carbon is burnt in the presence of 32 g of oxygen, how much carbon dioxide will be formed?
Q 36.
State Law of constant proportions. Explain with an example.
Q 37.
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 38.
Fill in the blanks:
___________ is the combining capacity of an element.
Q 39.
Name the international organization who approves names of elements.
Q 40.
How will you define chemical symbol?
Q 41.
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 42.
Fill in the blanks:
According to law of definite proportions, in a chemical substance the elements are always present in __________ proportions by mass.
Q 43.
Fill in the blanks:
According to Dalton's atomic theory, atoms of different elements differ in ______, size and chemical properties.
Q 44.
Give four examples of diatomic molecules.
Q 45.
What are polyatomic ions? Give examples?
Q 46.
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 47.
How many atoms are present in a
(i) H
2S molecule and
(ii) PO
43- ion?
Q 48.
Define mole. What is its significance?
Q 49.
Who introduced the term 'mole' in chemistry?
Q 50.
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)?
