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Define the atomic mass unit.
How many atoms are present in one molecule of aluminium sulphate?
Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass?
What is an atom?
Which postulate of Dalton’s atomic theory can explain the law of definite proportions?
Calculate the molar mass of the sulphur and phosphorus molecule.
Give Reasons for the Following:
Why is incorrect to say that, ’atoms are indivisible particles’?
Atoms of most elements are not able to exist independently. Then how these atoms form the matter that we can feel, see or touch?
It is said that molecules of many elements, such as argon (Ar), helium (He), neon (Ne), etc., are made-up of only one atom of the element. Why is it so?
The atoms of elements such as helium, neon, argon, radon, etc., do not form ions easily. Why is it so?
Why valency of an element is considered very important?
Give differences between an atom and an ion.
Differentiate between the cation and an anion.
What is meant by:
(a) Molecular mass
(b) Chemical formula
Give the main postulates of Dalton ’s atomic theory.
Explain giving a suitable example:
Law of conservation of mass.
Law of constant proportions.
Give the formula of the following compounds:
(i) Magnesium bicarbonate.
(ii) Cupric oxide.
(iii) Ferric oxide.
(iv) Ammonium hydroxide.
(v) Calcium carbonate.
(vi) Potassium carbonate.
What rules are to be kept in mind while writing a chemical formula?
What is the mass (in gram) of :
1 atom of oxygen
1 atom of sodium?
Which has more number of atoms:
100 grams of Magnesium or 100 grams of Aluminium
(Given: At mass of Mg=24 u, AL = 27 u)
Calculate the number of molecules of sulphur (S8) present in 64 g of solid sulphur. (Given: At. Mass of S=32 u)
Calculate the number of aluminium ions present in 0.051 g of aluminium oxide. (Given: At. Mass of AL = 27 u)
Calculate the number of moles present in:
(i) 92 grams of sodium
(ii) 108 grams of aluminium.
Calculate number of atoms present in:
(i) 0.1 mole of sulphur.
(ii) 2 moles of phosphors.
Mass of one atom of oxygen is:
3.42 of sucrose is dissolved in 18 g of water in a beaker. The number of oxygen atoms in the solution are:
A change in the physical state can be brought about:
In a compound such as water, the ratio of the mass of hydrogen to the mass of oxygen is always:
Which of the following postulates of Dalton’s atomic theory is challenged by the next generation scientists?
Which of the following represents 14 u?
The symbols of calcium, carbon and copper are:
The unit accepted for taking mass of atom and molecule is:
Which of the following would weigh the highest?
Which of the following has maximum numbers of atoms?
Which of the following contains maximum number of molecules?
The molecule having an atomicity of 4 is :
The molecular formula of aluminium sulphate is:
The chemical symbol for nitrogen gas is:
The chemical symbol for sodium is:
Which of the following correctly represents 360 g of water?
i. 2 moles of H2O
ii. 20 moles of water
iii. 6.022 x 1023 molecules of water
iv. 1.2044 x 1025 molecules of water
Which of the following statements is true about an atom?
One mole of H2O means:
i. 18 g of H2O
ii. 6.022 x 1023 molecules of H2O
iii. 180 g of H2O
iv. 1.8 of H2O
A molecule can be defined as the:
Which of the following will have maximum mass?
Write true or false for the following statements:
Oxygen molecule exists in the form of three molecules as O2, O3 and O4.
Sodium shows valency of Na+ and Na2+.
Iron shows valency of Fe2+ and Fe3+.
The formulae of cupric oxide and cuprous oxide are CuO and Cu2O respectively.
The elements having one valency are called monovalent.
A group of atoms carrying a charge are called bivalent ions.
Atomicity of phosphorus is 5 and that of sulphur is 6.
A mole always represents 6.023 x 1022 atoms or molecules or ions of a substance.
A mole always represents for gases, 22.4 litres of volume at 0°C and 1 atmospheric pressure which is known as standard temperature and pressure (STP).
Mass of two moles of atoms or molecules is called molar mass.