Question

You dissolve 5 g KCl in a total volume of 200 mL. What is the final [KCl]?

Answer 1

Ans- The final concentration is in terms of molarity. To get the concentration or molarity we use the following formula-

M = ( n / V ) X 1000

where, M is molarity or concentration

n is the number of moles

V is the total volume in ml

So to first find the number of moles,

n = m / M_{​​​​​​w}   ( m- mass of KCl and M_{​​​​​​w} - molecular weight of KCl)

n = 5/ 74.5

Now putting this value onthe first equation to find molarity,

M = {(5/74.5)/ 200 } X 1000

M = (0.06 X 1000) / 200

M = 0.3 mol/ ml

This is the concentration of the KCl.

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