Question

Write the molecular formula of the following: i) Hydrogen chloride iv) Calcium carbonate vii) Copper hydroxide x) Sodium carbonate Q2) Calculate the relative molecular mass of HNO3 (H=1, N=14, O=16) Q3) Calculate the number of moles for the following: (i) 52 g of He (finding mole from mass) (At. Mass of He = 4) (ii) 12.044 × 1023 number of He atoms (finding mole from number of particles). Q4) Define : i) Atom ii) Molecule iii) Molecular mass iv) Isotopes v) Valency ii) Aluminium oxide v) Zinc sulphate iii) Magnesium chloride

Answer 1

Answer:

i) HCl

iv) CaCO3

vii)Ch(OH)2

x)Na2CO3

Q3)

(i) 13

(ii) 2

Q4)

i) An atom is the smallest particle of an element, which can take part in chemical reactions.

ii) A molecule is a smallest particle of an element having an independent existence.

iii) Molecular mass is the number of times a molecule is heavier than 1/12 the mass of one atom of carbon.

iv) Isotopes are the atoms of elements having same atomic number but different mass number.

v) Valency is the combining capacity of an element. It is the number of hydrogen atoms an element can combine with or displace to attain stability.

ii) Al2O3

v) ZnCO3

iii) MgCl2