8/2/2019 Tutorial Water Chemistry 112

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SBK3

1. The formation of ice dur 

winter. Why?

2. Give one example to de

 

3. In Europe, engineers d

small gap to prevent th

account for this design?

4. Identify the type of bondi

more than one type, nam

5. How many water molecul

glyceraldehyde, shown h

 

6. Calculate the pH of the f 

i. 5 x 10-4 M

ii. 1 x 10-4 M

iii. 3 x 10-2 M

iv. 7 x 10-5 M

7. Calculate the [ H+ ] and [

i. Saliva,

ii. Intrac

iii. Tomat

iv. Grape

TUTORIAL

013 PRINCIPLE IN BIOCHEMISTRY

WATER CHEMISTRY

12/3/2012

ing colder weather helps to temper the seas

onstrate the property of water cohesion and a

sign city sidewalks using blocks of concrete

m from cracking. What property of water is

riefly explain your answer.

g between each pair of atom and molecules. I

e the type of bonding indicated by arrow.

es could hydrogen bond directly to the one mol

ere?

llowing aqueous solutions:

HCl

NaOH

KOH

NaOH

OH- ], for each of the following materials: 

pH 6.5

llular fluid of liver, pH 6.9

o juice, pH 4.3

ruit juice, pH 3.2

nal transition to

hesion.

separated by a

being taken into

examples with

ecule of 

8/2/2019 Tutorial Water Chemistry 112

http://slidepdf.com/reader/full/tutorial-water-chemistry-112 2/2

 

8. What is the [ CH3COO- ]/ [ CH3COOH ] ratio in an acetate buffer at the following pH:

a. pH 4.00?

b. pH 5.00? 

9. What is the pH of a buffer solution that contains:

a. 75% lactate form and 25% lactic acid?

b. 25 ml of 1.0 M lactic acid and 75 ml of 1.0 M sodium lactate.

10. Calculate the pH of a buffer solution that contains:

a. 0.10 M acetic acid and 0.25 M sodium acetate.

b. 10% acetic acid and 90% sodium acetate.

11. If the internal pH of a muscle cell is 6.8, what is the [ HPO42- ]/ [ HPO4

- ] ratio in this cell?

12. Suggest a suitable buffer range for each of the following substances:

a. Lactic acid and its sodium salt

b. Acetic acid and its sodium salt

13. You need to carry out an enzymatic reaction at pH 8.7. There are only two weak acids

available in the lab, one with a pKa of 8.3 and one with a pKa of 6.8.

a. Which substance and its conjugate base will you choose to make a suitable

buffer? Explain your reason.

b. What would be the ratio of the conjugate base/ conjugate acid of the buffer made

from the weak acids?

14. The pH of normal rainwater is approximately 5.6. The slight acidity compared to pure

water is caused by dissolved CO2. In some regions of the world, the acidity of rain has

increased to a pH of approximately 3.5.

a. Compare the hydrogen ion concentration [H+] in acid rain and the normal

rainwater?

b. Calculate the ratio of bicarbonate to carbonic acid in normal rainwater and in acid

rain.

c. Assume that acid rain has lowered the pH of a lake to pH 5.0. What is the

hydroxide ion (OH-) concentration of this lake?

15. a. Briefly explain what is monoprotic acid and polyprotic acid.

b. Draw the titration curve for each of the following acids. Assume they are titrated

with NaOH. Indicate the pKa and inflection point of each acid.

i. Benzoic acid

ii. Malic acid

iii. Citric acid

Please do the tutorial individually. Pass up the tutorial next week during lecture 19/3/2012.