Calculate the number of electrons which together weigh one gram.
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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 X 10-27 kg).

(a)  1 g atom of carbon = 14g
                               = 6.022 x 1023 atoms
   Each carbon atom 
     


(b) Mass of 1 neutron = 1.675 x 10-27 kg
    Mass of 2.4088 x 1021 neutrons
      = (1.675 x 10-27kg) x (2.4088 x 1021)
      = 4.0347 x 10-6kg

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Write the complete symbol for the atom with the given atomic number (Z) and atomic number (A).
(i) Z = 17,   A = 35 
(ii) Z = 92,  A = 233
(iii) Z = 4,   A = 9.


(i) The element with atomic number 17 is Cl. Its symbol is 
(ii) The element with atomic number 92 is U. Its symbol is 
(iii) The element with atomic number 4 is Be. Its symbol is 

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Calculate the number of electrons which together weigh one gram.


Mass of one electron =9.10939 x 10-31 kg

Therefore, Number of electrons that weigh 9.10939 x 10-31 kg =1


Number of electrons that will weigh1g= (1x10-3kg)

=0.1098 X10-3+31

=0.1098 X1028

=1.098 X1027

 


                

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Calculate the mass and charge of one mole of electrons.


One mole of electron
                     
Mass of 1 electron = 
Mass of 
                   
Charge on one electron
           
Charge on one mole electrons
             

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Calculate the total number of electrons present in one mole of methane.


1 molecule of  contains electrons = 6 + 4 = 10

                                     

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