Topic 12 Acid- base equilibria
Transcript of Topic 12 Acid- base equilibria
![Page 1: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/1.jpg)
Topic 12Acid- base equilibria
Week 5 - 4 May 2020, to complete by Friday 8 May.
![Page 2: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/2.jpg)
This week we are continuing Topic 12 – Acid Base Equilibria.
Please work your way through the powerpoint and make notes on each slide – youwill need your scientific calculator – if you need any help with the particularcalculator function buttons please get in touch.
This work will account for the 2 hours you would normally spend on my lessons.
By Friday – please do the attached question sheet to return to me:
Either take a photo of your work and email it to me, or send your answers viaa word document, again via email.
Good Luck!
![Page 3: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/3.jpg)
Specification points for this section…
![Page 4: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/4.jpg)
pH of strong acids
• Objectives:
• To know the difference between a strong and weak acid.
• To know the definition of pH.
• To understand what is meant by a monoprotic and a diprotic acid.
• To be able to calculate pH of a strong acid from hydrogen ion concentration and vice versa.
• To understand what the ionic product of water is.• To be able to calculate pH for a strong base using Kw.
![Page 5: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/5.jpg)
Starter
![Page 6: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/6.jpg)
• What is the difference between a strong and a weak acid?
• Write out an equation to illustrate a weak and a strong acid dissociating.
(Use HCl and CH3COOH as examples).
• Write the balanced chemical equation for the reaction between potassium carbonate and sulphuric acid. State symbols not needed.
• Ionic equation?
What can you remember from Year 11?
![Page 7: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/7.jpg)
• What is the difference between a strong and a weak acid?
• A strong acid fully dissociates in water whereas a weak acid only dissociates to a slight extent.
• Write out an equation to illustrate a weak and a strong acid.
• Write the balanced chemical equation for the reaction between potassium carbonate and sulphuric acid. State symbols not needed.
• K2CO3 + H2SO4 K2SO4 + H2O + CO2
• Ionic equation?
• CO32- + 2H+
H2O + CO2
Notice the different symbols
needed for the arrows
![Page 8: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/8.jpg)
Try these exam questions….
![Page 9: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/9.jpg)
Try these exam questions….
C – can you explain
why?
![Page 10: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/10.jpg)
![Page 11: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/11.jpg)
D
![Page 12: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/12.jpg)
pH of strong acids
• Objectives:
• To know the difference between a strong and weak acid.
• To know the definition of pH.
• To understand what is meant by a monoprotic and a diprotic acid.
• To be able to calculate pH of a strong acid from hydrogen ion concentration and vice versa.
![Page 13: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/13.jpg)
Hydrochloric acid and nitric acid are strong acids and ionise fully.
![Page 14: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/14.jpg)
HCl and HNO3 are monoprotic acids because they can donate one proton per
molecule. (mono = one)
![Page 15: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/15.jpg)
Sulphuric acid is also a strong acid and ionises fully. It is a diprotic acid because it
can donate two protons per molecule.
![Page 16: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/16.jpg)
Extra background information….
![Page 17: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/17.jpg)
pH of strong acids
• Objectives:
• To know the difference between a strong and weak acid.
• To know the definition of pH.
• To understand what is meant by a monoprotic and a diprotic acid.
• To be able to calculate pH of a strong acid from hydrogen ion concentration and vice versa.
![Page 18: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/18.jpg)
We can calculate the pH of a solution if its hydrogen ion concentration is known.
This is how we work out pH using the hydrogen ion concentration.
The [] show it’s a concentration.
You need to use the ‘log’ button on your calculator.
(not the Ln button as that’s a different type of log!!)
![Page 19: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/19.jpg)
![Page 20: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/20.jpg)
We can also rearrange the
equation to find H+
concentration if pH is known….s
(on your calculator you would
use ‘shift and log’ to do this – to
get the ‘10x’ function.
![Page 21: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/21.jpg)
For a strong monoprotic acid like hydrochloric acid, the hydrogen ion concentration
is equal to the concentration of the acid itself – because every acid molecule is
thought to dissociate to a H+.
![Page 22: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/22.jpg)
Q What is the pH of 0.10 mol dm–3 hydrochloric acid?
![Page 23: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/23.jpg)
The hydrogen ion concentration will also be 0.10 mol dm–3.
This is because every HCl will produce 1 H+
So, now on your calculator, do:
‘-’ ‘log’ ‘0.1’ ‘=‘
(it’s the negative sign ‘-’ button, not minus!)
![Page 24: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/24.jpg)
A: The pH will be 1.0 for 0.10 mol dm–3 hydrochloric acid.
Hopefully you get the answer ‘1’!!
(no units needed for pH)
![Page 25: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/25.jpg)
For a strong diprotic acid like sulfuric acid, the hydrogen ion concentration is
equal to twice the concentration of the acid itself.
![Page 26: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/26.jpg)
What is the pH of 0.10 mol dm–3 sulphuric acid? The hydrogen ion concentration
will be 0.20 mol dm–3.
![Page 27: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/27.jpg)
The pH will be 0.69 for 0.10 mol dm–3 sulphuric acid.
![Page 28: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/28.jpg)
What is the hydrogen ion concentration in nitric acid with a pH of 1.7?
![Page 29: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/29.jpg)
Substitute the pH into the equation. Remember to enter ‘minus pH’ when you use a
calculator.
![Page 30: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/30.jpg)
The hydrogen ion concentration for nitric acid with a pH of 1.7 will be 0.02 mol dm–3.
As it is a strong monoprotic acid, this will also be the concentration of the nitric acid
itself.
(on your calculator – ‘shift’ ‘log’ (to get 10x) then ‘-’ ‘1.7’)
![Page 31: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/31.jpg)
Worked examples to review:
![Page 32: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/32.jpg)
![Page 33: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/33.jpg)
![Page 34: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/34.jpg)
• Now have a go at these questions:
![Page 35: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/35.jpg)
• Answers
16a)pH = 1.00 b) pH = 2.00 c) pH = 3.00
17 pH = 1.09
18a)5.01 10−4 mol dm−3
b) 3.98 10−6 mol dm−3
c) 1.99 10−7 mol dm−3
d) 3.16 10−11 mol dm−3
![Page 36: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/36.jpg)
Now have a go at the following exercises to practise:
![Page 37: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/37.jpg)
3
2
8
0.3
0.6
0.2
0.2
0.08
0.16
0.35
![Page 38: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/38.jpg)
![Page 39: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/39.jpg)
3.00 -0.17 3.60 11.35
0.0018 5.01x10-41.20x10-14 0.014 5.01
![Page 40: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/40.jpg)
You may need to work through how pH is affected by dilution:
![Page 41: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/41.jpg)
![Page 42: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/42.jpg)
![Page 43: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/43.jpg)
For Q3, concentration is moles
vol in dm3
![Page 44: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/44.jpg)
![Page 45: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/45.jpg)
pH of strong acids
• Objectives:
• To know the difference between a strong and weak acid.
• To know the definition of pH.
• To understand what is meant by a monoprotic and a diprotic acid.
• To be able to calculate pH of a strong acid from hydrogen ion concentration and vice versa.
• To understand what the ionic product of water is.• To be able to calculate pH for a strong base using Kw.
![Page 46: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/46.jpg)
![Page 47: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/47.jpg)
![Page 48: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/48.jpg)
Units of Kw?
mol2 dm-6
![Page 49: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/49.jpg)
![Page 50: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/50.jpg)
![Page 51: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/51.jpg)
![Page 52: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/52.jpg)
19 a) Ionisation is endothermic.b) Extent of ionisation increases as the temperature rises and the
hydrogen ion concentration rises as the temperature rises. The number value of the pH falls.
c) No, because [H+(aq)] always equals [OH−(aq)].20 a) pH = 14.00
b) pH = 12.30 c) [OH−] in 0.0010 mol dm−3 Ba(OH2) = 2 × 0.0010 mol dm–3
So [H+(aq)] = = 5.0 × 10−12 mol dm–3
pH = 11.30
12 Acid–base equilibria
14 2 6
3
1.0 10 mol dm
2 0.0010 mol dm
© Andrew Hunt, Graham Curtis 2015
![Page 53: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/53.jpg)
Plenary
© Andrew Hunt, Graham Curtis 2015
![Page 54: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/54.jpg)
© Andrew Hunt, Graham Curtis 2015
![Page 55: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/55.jpg)
© Andrew Hunt, Graham Curtis 2015
![Page 56: Topic 12 Acid- base equilibria](https://reader030.fdocuments.us/reader030/viewer/2022012715/61ad64c6e783e963e15ae5ba/html5/thumbnails/56.jpg)
Well done!
Now complete the homework task and remember to send a copy of your answers back to me by Friday 8 May.