Question

What is the charge of 96 amu of $ {S^{2 - }} $ ?
(A) $ 2C $
(B) $ 3.2*{10^{ - 19}}C $
(C) $ 9.6*{10^{ - 19}}C $
(D) $ 6C $

Answer 1

Hint : The atomic mass of sulphur is 32 amu. Each sulphide ion has two negative charges present in it. We have to find out what the total charge here is by using this information given and known to us. To get the charge on the ion we will use following formulas as:
Number of ions = given mass/atomic mass
Total charge = Number of ions * number of charge on ion * one electron’s charge

Complete Step By Step Answer:
We know that the atomic number of Sulphur is 16 and its atomic mass is 32 amu.
Now, we have to find out how many Sulphur ions are present in 96 amu.
For this first we will calculate the number of ions as:
Number of ions = given mass/atomic mass= $ \dfrac{{96amu}}{{32amu}} = 3 $
Here, we can see that the ion is represented as $ {S^{2 - }} $ . That means each sulphide ion has 2 negative charges present in this ion.
As we know that 1 electron has charge = $ 1.602*{10^{ - 19}}C $
Total charge of the sulphide ion represented here =
  $ 3*2*1.062*{10^{ - 19}} $
            = $ 9.6*{10^{ - 19}}C $
Hence, option (C) is the correct option that is the total charge present on the sulphide ion with given mass of 96 amu is $ 9.6*{10^{ - 19}}C $ .

Note :
Using the above method that is to find the number of ions we should always remember that formula that is atomic mass which is given divided by atomic mass. Then the number of ions with charge on the ion with one electron charge then we will get the final total charge on the ion given. By using this technique we can solve all these types of questions.