Do we need to memorise the pH at which indicators change colour? (1 Viewer)

[Carl5]

e.g. Litmus, phenolphthalein, bromothymol blue, methyl orange?

 

[RANK 1]

e.g. Litmus, phenolphthalein, bromothymol blue, methyl orange?

yes

 

[Shadowdude]

Unfortunately, yes. Though at most it'll probably just be one multiple choice question.

 

[Carl5]

Damn. I don't get why stuff like this gets tested. I always thought chem would be more about application and less about memorisation. Sure, we have to apply it after memorising, but why would anyone memorise these in real life when they could just have them written down... less likely to make errors.

 

[hscishard]

damn what other figures do we have to memorise?

 

[zhiying]

The syllabus has a dot point that requires it I think. But seriously most times they give you a giant table with all the values and you just have to read it off. Seems like only time it asks you to recall the values is in titration questions, when they ask you what indicator is suitable for this titration etc. Other figures that needs to be memorised off the top of my head are....the volume of gas at room temp, heat capacity of water (4.18), and preferably the energy released in Haber process (-92kJ/mol)

 

[DVDVDVDV]

A better answer is "sort of"

You need to know acid/base results but not the end point of each indicator.

 

[b3kh1t]

The syllabus has a dot point that requires it I think. But seriously most times they give you a giant table with all the values and you just have to read it off. Seems like only time it asks you to recall the values is in titration questions, when they ask you what indicator is suitable for this titration etc. Other figures that needs to be memorised off the top of my head are....the volume of gas at room temp, heat capacity of water (4.18), and preferably the energy released in Haber process (-92kJ/mol)

on the information sheet given in the exam the volume of gas at room temperature (25*C) and also at 0*C are given, and also the heat capacity of water, ie 4.18. Although it is important you know how to use them. Something in acidic environment that I would recommend you learn is approximately three examples of esters, such as pentyl ethanoate is pear, ethyl butanoate is pineapple and ethyl ethanoate is rum.

With the indicators, the main ones that you need to know are;
methyl orange (goes from red to orange to yellow, changing at 3.1-4.4)
bromothymol blue (goes from yelloww to green to blue, changing at 6.2-7.6)
phenolphthalein (goes from colourless to pink to red or purple in the more basic solution, from 8.3-10)