Question

1. A piece of Cu weight 0.635 gm. how many atom of
Cu does it contain ?
(a) 6.02 x 1021
(b) 6.02 x 1023
(c) 6.02 x 1022
(d) 6.02 x 1020
2. Calculate the weight of 12.044 x 1023 atoms of C
(a) 6 gm
(b) 12 gm
(c) 18 gm
(d) 24 gm
3. One atom of an element X weight 6.644 10-23
gin. Calculate the number of gm-atom (mole) in 40
kg of it
(a) 10
(b) 102
(d) 104
(c) 103
12
:
10​

Answer 1

Answer:

1. a

2. d

3. c

Explanation:

Hey.

Here is the answer.

1. Gram-atomic mass of copper=63.5g  

Number of moles in 0.635g of copper = 0.635/63.5

⇒0.01

Number of copper atoms in 0.01 moles =0.01×6.02×1023

⇒6.02×1021

2. No. of moles of Carbon atoms

= No. of atoms(Avogadro constant)

= 12.044 × 1023/6.022 × 1023

= 2 mole

Mass of carbon atoms = No. of moles × atomic mass

= 2 × 12

= 24 g

3. weight of 1 atom = 6.644×10^-23 g

so, no. of atoms in 40 kg  

= 40×10^3 / 6.644×10^-23

= 6.02046 × 10^26 atoms

As, 1 gram atom = no. atoms in one mole = 6.02×10^23

so, no. of gram atom = 6.02046×10^26/6.02×10^23

=1000 gram atoms