Question

a) Write the chemical formulae for the following and calculate their molecular masses -
1) Sodiumoxide ii) Magnesiumcarbonateiii) Potassiumchloride
(sodium=23uOxygen=16u,Carbon=12u, Magnesium=24u,Chlorine=35.5u potassium =39u


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Answer 1

$\bold{(1)Sodium \: oxide}$.

Sodium has valency +1 and of oxygen is -2 .So, two sodium atoms loses there two electrons to oxygen and forms sodium oxide.

$\large \boxed{Na_2O}$

MOLECULAR MASS = 2Na + O

= 2 × 23 + 16

= 46 + 16

$\large \boxed{62 \: u}$

$\bold{(1)Magnesium \: carbonate }$.

Magnesium has valency +2 and of carbonate is -2 .When they react magnesium loses it two electrons to carbonate and forms magnesium carbonate.

$\large \boxed{MgCO_3}$

MOLECULAR MASS = Mg + C + 3(O)

= 24 + 12 + 3 × 16

= 24 + 12 + 48

$\large \boxed{84 \: u}$

$\bold{(3)Potassium \: chloride}$.

Potassium have valency + 1 and chlorine have valencely -1 .When they react potassium loses its two electrons to chlorine and forms potassium chloride.

$\large \boxed{KCl}$

MOLECULAR MASS = K + Cl

= 39 + 35.5

$\large \boxed{74.5 \: u}$

Answer 2

Answer:-

☆ Sodium Oxide.

Na2O

=) Molecular Mass = 2 × Na + O

=) Molecular Mass = 2 × 23u + 16u

=) Molecular Mass = 46u + 16u

=) Molecular Mass = 62u.

☆ Magnesium Carbonate.

MgCO3.

=) Molecular Mass = Mg +C + 3 × O

=) Molecular Mass = 24u + 12u + 3× 16u

=) Molecular Mass = 36u + 48u

=) Molecular Mass = 84u.

☆ Potassium Chloride.

KCl

=) Molecular Mass = k + Cl

=) Molecular Mass = 39u + 35.5u

=) Molecular Mass = 74.5u