Question

Convert into mole.
a)12g of oxygen gas
b)20g of water c)22g of carbon dioxide.

Answer 1

(a) Molecular weight of oxygen in grams = 32 g

Thus, 12 g of oxygen=

 1/32×12

=0.375 moles

(b) Molecular weight of water (H2O) in grams= 2+ 16=18g

=one mole of water

Thus, 20 g of water= 1/18×20

=1.111 moles

(c) Molecular weight of carbon dioxide (CO2) in grams

=12+2×16=44 g

=one mole of carbon dioxide

Thus, 22 g of carbon dioxide = 1/44×22

=0.5 moles

hope it helps :)

Answer 2

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(a) 12g of oxygen gas

➝ Molar mass of oxygen gas = 32g

$\rm\longrightarrow\:\dfrac{1}{32}\:mole=1g$

$\rm\longrightarrow\:\dfrac{12}{32}\:mole=12g$

$\rm\longrightarrow\:0.375\:mole=12g$

$\rm\longrightarrow\:12g=0.375\:mole$

(b) 20g of water

➝ Molar mass of Water = 18g

$\rm\longrightarrow\:\dfrac{1}{18}\:mole=1g$

$\rm\longrightarrow\:\dfrac{20}{18}\:mole=20g$

$\rm\longrightarrow\:1.11\:mole=20g$

$\rm\longrightarrow\:20g=1.11\:mole$

(c) 22g of carbon dioxide

➝ Molar mass of carbon dioxide = 44g

$\rm\longrightarrow\:\dfrac{1}{44}\:mole=1g$

$\rm\longrightarrow\:\dfrac{22}{44}\:mole=22g$

$\rm\longrightarrow\:0.5\:mole=22g$

$\rm\longrightarrow\:22g=0.5\:mole$

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➝ Mass number :- The sum of neutrons and protons present in the nucleus of an atom is called mass number.It is denoted by A

➝ Mass Number = No.of neutrons + No.of Protons

or, A = n + p