1.Calculate the total number of electrons present in one mole of methane.
2. Find the total number and the total mass of neutrons in 7 mg of C14.
3. Find the total number and the total mass of protons in 34 mg of NH3 at STP.
Will the answer change if the temperature and pressure are changed.
Answers
(i)number of electrons present in 1 mole of methane(CH4); {1(6)+4(1)}=10
Number of electrons present in 1 mole i.e.6.023×10²³ molecules of methane=6.022×10²³×10=6.022×10²⁴
(ii) (a)number of atoms of 14 c in one mole 6.023*10 power 23 Since 1 atom of 14 c contains (14-6) i.e., 8 neutrons,the no. of neutrons in 14g of 14 c is (6.023*10 power 23)*8. Or,14g of 14 c contains (6.022*10 power 23*8)neutrons. Numbers of neutrons in 7mg = (6.022*10 power 23*8*7mg)/1400mg= 2.4092*10 power 21 (b) Mass of 1 neutron = 1.67493*10 power -27kg Mass of total neutrons in 7g of 14 c = (2.4092*10 power 21)(1.67493*10 power -27)=4.0352*10 power -6 kg
(iii) (a) 1 mole of NH3={1(14)+3(1)}=17g if NH3=6.022*10 power 23 molecules of NH3 Total no. of Protons present in 1 mole of NH3={1(7)+3(1)}=10 no. of protons in 6.022*10 power 23 molecules of NH3=(6.022*10 power 23)*10=6.022*10 power 24 17g of NH3 contains (6.022*10 power 24)protons Number of protons in 34mg of NH3=(6.022*10 power 24*34mg)/17000mg=1.2046*10 power 22 (b) mass of 1 proton =1.67493*10 power -27kg total mass of proton in 34mg of NH3=(1.67493*10 power -27kg)(1.2046*10 power 22)=2.0176*10 power -5kg
The no. of protons, neutrons & electrons in an atom is independent of temperature and pressure conditions.
Hence the obtained value will remained unchanged if the temprature and pressure is changed.