Question

Q.no. 12 plz answer it

Answer 1

Hey frnd!





Deepa Paikar asked in Chemistry

Find (a) the total number and (b) the total mass of neutrons in 7 mg of 14C.

(Assume that mass of a neutron = 1.675 × 10–27 kg).

 7

 Follow0



Kirti Gogia answered this
3497 helpful votes in Chemistry, Class XI-Science

The molar mass of 14C is 14g. Therefore we will first calculate the number of moles in 7mg (or 0.007 g) of 14C.

Number of moles in 0.007 g of 14C = mass / molar mass

= 0.007 / 14 = 0.0005 moles

Now 1 mole of 14C = 6.023 X 1023 atoms of 14C

Therefore 0.0005 moles of 14C = 0.0005 X 6.023 X 1023 atoms of 14C

= 3.015 X 1020 atoms of 14C

Now 1 atom of 14C contains 6 protons (atomic number of Carbon is 7).

Therefore there are 8 neutrons present in 1 atom of 14C.

Thus 1 atom of 14C = 8 neutrons

Therefore

3.015 X 1020 atoms of 14C = 8 X 3.015 X 1020neutrons of 14C

  = 2.412 X 1021 neutrons of 14C

Now mass of 1 neutrons = 1.675 X 10-27 Kg

Therefore mass of 2.412 X 1021 neutrons of 14C = 2.412 X 1021 X 1.675 X 10-27 Kg

  = 4.04 X 10-6 Kg

Hope it helps