Question

What mass of potassium hydroxide (KOH) is present in 300cm³ of 0.1 mol/dm³ solution of KOH​

Answer 1

First convert cm3 to dm3 so that there both the same unit.
Must divide by 1000
300cm^3÷1000
0.3dm^3

Then use the formula C=n/V
C=concentration
n=moles
V=volume

0.1=n/0.3
nKOH=0.03

Then change to grams.
use formula
n=m/M

n=moles
m=mass in grams
M=molar mass.
0.03=m/56
mKOH=1.68g

Molar mass of KOH from periodic table= 39+16+1=56g/mol