Question

Calculate the number of moles lo
Section C (2:5-10)
10. Calculate the number of particles in each of the following
(1)12 g of Na atoms (in)25 g of O, molecules (11) 2 mole of carbon atoms​

Answer 1

$\LARGE\underline{\pink{\sf{Required\:answer:-}}}$

Number of particles of a given substance is given by ,

$\boxed{ \sf{number \: of \: particles =n \times N_A}}$

Number of moles is given by ,

$\large\boxed{\sf{n=\dfrac{Given\:weight}{Atomic\:weight}}}$

(1) 12 g of Na

Given weight = 12 g

Atomic weight of Sodium = 23

Now , By applying the formula we get ;

⇛ $\sf{n=\dfrac{12}{23}}$

⇛ ${\sf{n=0.52\:mol}}$

Now , Number of particles is given by ;

⇛ Number of particles = 6.023 × 10²³ × 0.52

⇛ Number of particles = 3.13 × 10²³

━━━━━━━━━━━━━━━━━━━━━━━━

(2) 25 g of O molecule

Given weight = 25 g

Atomic weight of Oxygen molecule = 32

Now , By applying the formula we get ;

⇛ $\sf{n=\dfrac{25}{32}}$

⇛ ${\sf{n=0.78\:mol}}$

Now , Number of particles is given by ;

⇛ Number of particles = 6.023 × 10²³ × 0.78

⇛ Number of particles = 4.697 × 10²³

━━━━━━━━━━━━━━━━━━━━━━

(3) 2 moles of carbon atoms

Number of moles = 2

Now , Number of particles is give by ;

⇛ Number of particles = 6.023 × 10²³ × 2

⇛ Number of particles = 12.046 × 10²³

$\LARGE\underline{\pink{\sf{Note:-}}}$

$\sf{N_A}$ is avogadro number.

Answer 2

\LARGE\underline{\pink{\sf{Required\:answer:-}}}

Requiredanswer:−

Number of particles of a given substance is given by ,

\boxed{ \sf{number \: of \: particles =n \times N_A}}

numberofparticles=n×N

A

Number of moles is given by ,

\large\boxed{\sf{n=\dfrac{Given\:weight}{Atomic\:weight}}}

n=

Atomicweight

Givenweight

(1) 12 g of Na

Given weight = 12 g

Atomic weight of Sodium = 23

Now , By applying the formula we get ;

⇛ \sf{n=\dfrac{12}{23}}n=

23

12

⇛ {\sf{n=0.52\:mol}}n=0.52mol

Now , Number of particles is given by ;

⇛ Number of particles = 6.023 × 10²³ × 0.52

⇛ Number of particles = 3.13 × 10²³

━━━━━━━━━━━━━━━━━━━━━━━━

(2) 25 g of O molecule

Given weight = 25 g

Atomic weight of Oxygen molecule = 32

Now , By applying the formula we get ;

⇛ \sf{n=\dfrac{25}{32}}n=

32

25

⇛ {\sf{n=0.78\:mol}}n=0.78mol

Now , Number of particles is given by ;

⇛ Number of particles = 6.023 × 10²³ × 0.78

⇛ Number of particles = 4.697 × 10²³

━━━━━━━━━━━━━━━━━━━━━━

(3) 2 moles of carbon atoms

Number of moles = 2

Now , Number of particles is give by ;

⇛ Number of particles = 6.023 × 10²³ × 2

⇛ Number of particles = 12.046 × 10²³

\LARGE\underline{\pink{\sf{Note:-}}}

Note:−

\sf{N_A}N

A

is avogadro number.