有幾題化學題想問大家(快)

2008-03-27 11:00 am

1.點解燒KNO3唔會form solid oxide既?
2.which of the following solution is a weak electrolyte?
A.0.1M glucose solution
B.2M propanoic acid
C.0.5M NH4Cl solution
D.0.2M Na2CO3 solution
我想知點解b岩?

3.when a coin containing 92% silver and 8% copper is warmed with excess conc.nitric acid,it form?
A.clourless solution
B.pale blue solution
C.colourless solution with some undissole copper
D.pale blue solution with some undissole silver
我想知點解係b唔係a?

4.If gaseous hydrogen chloride is bubbled into fixed volume of dilute hydrochloric acid solution,which of the following are true?
(1)pH value of solution increase
(2)mass of sodium hydroxide required for complete neutralization of solution increase
(3)the conductivity of solution increase
點解2,3岩?但係第1個就唔岩?

更新1:

仲有呀,唔好意思 An aqueous solution of ethanoic acid has a pH value of 4.Which of the following substance when added to this solution,would increase its pH vlaue? (1)solid calcium carbonate (2)solid NaCl (3)aqueous ammonia (4)dilute sulphric acid A.1,3 B.1,4 C.2,3 D.2,4 我想知點解1岩但係2唔岩?

回答 (1)

用戶7369

2008-03-27 6:04 pm

✔ 最佳答案

1. potassium salts and sodium salts are more stable than the other
metal salts. so the nitrate salt will form nitrite in stead of oxide.
2. although propanoic acid contains carboxylic group, when the
concentration is high , the covalent character is predonminate.
so less mobile ion is available. so it is a weak electrolyte.
3. copper will be oxidized to copper ii ion which is blue colour.
4. when the solution is more acidic, the pH will decrease.
since when hydrogen chloride is dissolved in water,
it will form hydrochloric acid. so the pH will decrease.
5. calcium carbonate will react with ethanoic acid to form
carbon dioxide and calcium ethanoate. the concentration
of hydrogen ion will decrease, so the pH value will increase.
but sodium chloride solution is neutral. so there should be
no change in pH value.

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