# Hard Titration Question (1 Viewer)

#### Mark433

##### New Member
Can anyone help with this question, part a isnt hard but part b has me stumped...

a)
A Hydrochloric acid solution was standardised by titrating 10ml of it against a 0.106 mol/L sodium hydroxide solution. The average titration volume was 35.6ml. Calculate the concentration of the HCl.

b)
A sample of Magnesium Oxide was found to be contaminated with the sodium chloride. Magnesium oxide is not very soluble in water but can be dissolved in an excess of the standardisted HCl

In order to determine the purity of the magnesium oxide, 3.86g of the sample was dissolved in 500ml of Hcl and then 50ml of the resulting solution was titrated against the NaOH solution of known concentration. The average titration volume was found to be 10.4ml.

Calculate the percentage of magnesium oxide in the concentration sample.

#### Riviet

##### .
HCl + NaOH -> NaCl + H2O

V(NaOH) = 35.6 - 10 = 25.6 ml = 0.0256 L

nNaOH=cV
=0.106 x 0.0256
=0.0027136 mol.

Sine ratio of number of moles of HCl to number of moles of NaOH is 1:1,

.'. n(HCl) = 0.0027136 mol.

.'. CHCl = n/V
=0.0027136 / 0.01 (10ml of HCl = 0.01 L)
=2.7136 mol/L

Hope that helps.

Last edited:

#### khanishka

##### New Member

can someone pls help me with this

#### Ledepressedrightnow

##### Active Member
How long did the question last? Did you spit or swallow?