Edexcel A2 Chemistry Exams -6CH04 (14th June) and 6CH05 (22nd June) Discussion Thread

Doesn't the sodium thiosulphate react with iodine to produce iodide ions and not the other way round?

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The pH of the 10cm^3 HCl is 0 as -log(1)=0. adding 10 cm^3 to 990cm^3 gives a volume of 1000cm^3. this increase in volume essentially dilutes the acid conc by a factor of 2. Because the sol of HCl has been diluted by factor 2, you add 2 to the initial pH, This gives an overall pH of the 1000cm^3 HCl sol of: 2


Hope that helps!

Work out moles of hcl first which is (10/1000 x 1) which is 0.01
This is added to 990cm^3, so new volume is 1000cm^3, you have to work work out concentration of hcl in new volume (n/v=c)
This is (1000/1000) x 0.01 which is still 0.01
And - log(0.01) is = 2.

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The pH of 3 solutions with concentration 1.0mol dm-3 was measured.
Solution 1 NH3
Solution 2 CH3COONa
Solution 3 NH4Cl
Which of the following shows the three solutions in order of increasing Ph?

A 1 2 3
B 3 2 1
C 3 1 2
D 2 3 1 Why is the correct answer B and not D?

can someone please tell how you find mol at eqilibrium for H2?

We know that all of the H2 has had to react to form the CH3OH; since CH3OH = 38.5 moles at equilibrium, H2 must be 77.5 - 38.5 = 39 moles

Does the sn2 or sn1 mechanism form a racemic mixture