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High School Chemistry
Titration
A titration of 25ml of sodium hydroxide of unknown concentration against 1M hydrochloric acid using methyl orange indicator
SafetySafety spectacles must be worn when carrying out the titration0.4M sodium hydroxide is labelled irritant1M hydrochloric acid is labelled irritantAny spillages should be washed off with copious amounts of water immediately
Methyl orange indicator colours
red in acid
yellow in alkali
orange at the endpoint
I describe the colour as peach in the video clip, but you should use the word orange in GCSE chemistry examinations
The video clip is a little jumpy due to my editing
Here's a revision calculation for GCSE Chemistry students
Using the following data obtained from the video clip, calculate the concentration of the sodium hydroxide solution
Table of results
Starting volume 2.4ml
End volume 12.4 ml
Titration volume 10.0ml
The end volume was possibly 12.45 or 12.5 ml but this was not as clear as it should have been on the video clip. This illustrates the need to carry out repeat titrations until two concordant results are obtained.
Two concordant results in this titration experiment would have been two titration volumes with the same value or within 0.1ml of each other.
Titration calculation
The titration equation is
NaOH + HCl = NaCl + H2O
Thus 1 mol NaOH = 1 mol HCl
Step 1 What were the number of moles of HCl used in the titration
Number of moles of HCl = concentration x volume in dm3
10 ml HCl = 0.01dm3 HCl
Number of moles of HCl = 1 x 0.01 = 0.01 mol
Step 2 From the titration equation
0.01 mol HCl = 0.01 mol NaOH
Step 3 What is the concentration of the NaOH
Concentration = number of moles NaOH / volume NaOH
25ml NaOH = 0.025dm3
Concentration = 0.01 / 0.025
= 0.4 M
0.4M = 0.4 mol / dm3
You Tube text descriptions do not allow brackets etc
The experiment was filmed using a smartphone in portrait orientation to facilitate revision on a smartphone