(i) Calculate the total number of electrons present in one mole of methane. (ii) 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). (iii) Find (a) the total number and (b) the total mass of protons in 34 mg of NH3 at STP. Will the answer change if the temperature and pressure are changed?
Answers
Answer:
1. 6.022 x 1024
2. a) 4088 x 1022
b) 4.0347 x 10-6 kg
3. a) 1.2044 x 1022 protons
b) 2.0145 x 10-5 kg
No.
Explanation:
1. Molecule of CH4 (methane) contains electron = 10
Therefore , by calculation, 1 mole (6.022 x 1023 atoms) contains electron = 6.022 x 1024
2. a) 1g atom of 14C = 14g = 6.022 x 1023 atoms = 6.022 x 1024 x 8 neutrons
Thus 14g or 14000 mg have 6.022 x 1024 x 8 neutrons
Therefore 7 mg will have neutrons = 6.022 x 1024 x 8 / 14000 x 7 = 2.4088 x 1022
b) mass of 1 neutron = 1.675 x 10-27 kg
Therefore mass of 2.4088 x 1021 neutrons = 2.4088 x 1021 x 1.67 x 10-27 = 4.0347 x 10-6 kg
3. a) 1 mol of NH3 = 17g NH3 = 6.022 x 1023 molecules of NH3 = (6.022x1023)(7 + 3) proton = 6.022 x 1024 protons
Therefore 34 mg i.e 0.034 g NH3 = 6.022 x 1024 x 0.034/1 = 1.2044 x 1022 protons
b) mass of 1 proton = 1.6726 x 10-27 kg
Therefore mass of 1.2044 x 1022 protons = (1.6726 x 10-27)(1.2044 x 1022) kg = 2.0145 x 10-5 kg
No, Certainly Not. The answer will not change with change in temperature and pressure as it is not relational with these factors in any way.