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Chemistry Form 4 • MODULE

EXERCISE / LATIHAN

1 The diagram below shows the set-up of apparatus to prepare soluble salt Y.
Rajah di bawah menunjukkan susunan radas bagi menyediakan garam larut Y.

Nitric acid
Asid nitrik

3
–3
25 cm of 1 mol dm potassium hydroxide solution
+ phenolphthalein
3
-3
25 cm larutan kalium hidroksida 1 mol dm + fenolftalein
3
Phenolphthalein is used as an indicator in a titration between nitric acid and sodium hydroxide solution. 25 cm of nitric
3
acid completely neutralises 25 cm of 1 mol dm potassium hydroxide solution. The experiment is repeated by reacting
–3
3
3
–3
25 cm of 1 mol dm potassium hydroxide solution with 25 cm nitric acid without phenolphthalein. Salt Y is formed
from the reaction.
Fenolftalein digunakan sebagai penunjuk dalam pentitratan antara asid nitrik dengan larutan kalium hidroksida. 25 cm asid nitrik
3
meneutralkan 25 cm larutan kalium hidroksida 1 mol dm . Eksperimen ini diulang dengan menindakbalaskan 25 cm larutan kalium
3
3
–3
hidroksida 1 mol dm dengan 25 cm asid nitrik tanpa fenolftalein. Garam Y terbentuk daripada tindak balas ini.
3
–3
(a) Name salt Y.
Nyatakan nama garam Y.
Potassium nitrate
(b) Write a balanced equation for the reaction that occurs.
Tuliskan persamaan seimbang bagi tindak balas yang berlaku.
HNO 3 + KOH KNO 3 + H 2 O
(c) Calculate the concentration of nitric acid.
Hitungkan kepekatan asid nitrik tersebut.
1
Mol of NaOH = 1 × = 0.025 mol
1 000
From the equation, 1 mol of KOH : 1 mol of HNO 3
0.025 mol of KOH : 0.025 mol of HNO 3
Concentration of HNO , M
3
25
0.025 = M ×
1 000
M = 1 mol dm –3
(d) Why is the experiment is repeated without phenolphthalein?
Mengapakah eksperimen ini diulang tanpa menggunakan fenolftalein?
To get pure and neutral salt solution Y.
(e) Describe briefly how a crystal of salt Y is obtained from the salt solution.
Huraikan secara ringkas bagaimana hablur garam Y diperoleh daripada larutan garamnya.
– The salt solution is poured into an evaporating dish.

– The solution is heated to evaporate the solution until one third its original volume// a saturated solution formed.
– The saturated solution is allowed to cool until salt crystals Y are formed.
– The crystals are filtered and dried by pressing them between filter papers.

(f) Name two other salts that can be prepared with the same method.
Namakan dua garam lain yang boleh disediakan dengan kaedah yang sama.
Potassium/sodium/ammonium salt. Example: potassium nitrate, sodium sulphate.

(g) State the type of reaction in the preparation of the salts.
Nyatakan jenis tindak balas dalam penyediaan garam ini.
Neutralisation

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