The tablet has a mass of 1.20 g and contains 700 mg of lithium carbonate. Calculate the percentage by mass of lithium carbonate in this tablet.

The right answer is "58.3%".

Explanation:

The given values are:

Mass of lithium carbonate,

= 700 mg

i.e.,

= 0.7 g

Mass of tablet,

= 1.20 g

Now,

The percentage of active ingredient will be:

=  

On substituting the given values, we get

=  

=  

=  %

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"