for step c - the calculation is:
CAVA/a = CBVB/b
The equation is: Na2CO3(aq?) + 2HCL(aq?) --> CO2(g) + H2O(l) + 2NaCl(aq)
Where:
CA = Concentration of Acid = Unknown (what we have to find)
VA = Volume of Acid (HCL) = 21.4mL = 0.0214L
CB = Concentration of Base = 0.1 mol/L
VB = Volume of Base = 25mL = 0.025L
a = coefficient of acid in equation= 2
b = coefficient of base in equation = 1
Note. All volumes must be in litres.
CA = (CB)(VB)(a)/(VA)(b)
CA = 0.2336448598... mol/L
CA = 0.234 mol/L (3 S.F)