Short Answer TypeUse the data given in the following table to calculate the molar mass of naturally occurring argon isotopes:
Isotope Isotopic molar mass Abundance
36Ar 35·96755 g mol–1 0·337%
38Ar 37·96272 g mol–1 0·063%
40Ar 39·9624 g mol–1 99.600%
Long Answer TypeCalculate the volume at STP occupied by:
(i) 16 g of oxygen
(ii) 2·5 moles of CO2
(iii) 1 × 1021 molecules of oxygen.
Short Answer TypeIf 1021 molecules are removed from 200 mg of CO2, then how many moles of CO2 are left?
What is the name of the element whose mass of one atom is 4×10–23. Given Avogadro’s number as 6×1023.
Long Answer TypeExplain the terms empirical and molecular formulae of a compound. How are these related to each other?
Empirical formula: The empirical formula is the formula of a compound which gives the simple whole number ratio of the atoms of various elements present in one molecule of the compound. For example, empirical formula of benzene is CH, which indicates that atomic ratio of C : H in benzene is 1 : 1.
Molecular formula: The formula which represents the actual number of atoms of various elements present in the molecule of a substance is known as molecular formula.
For example, the molecular formula of benzene is C6H6 which shows that in one molecule of benzene there are actually six carbon atoms and six hydrogen atoms.
Relation between empirical and molecular formulae:
Molecular formula is a whole number multiple of empirical formula and the two are related as:
Molecular formula = n × (Empirical formula) where n is an integer 1, 2, 3 .... and is given by
Short Answer TypeCalculate the mass percentage of different elements present in sodium sulphate (Na2SO4).
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