日八十月二年三七九一屦公年二十六國民華中育教坻割
郭日僑華
三期星
四笑張五第二日六廿月正年丑癸屬
WAH KIU YAT PO
2A1 + 301,
2A101
菠橋
1913英文中學會考試題預習專欄
That
化學科
(十九)
Valse To rimossan. Comme mi
Today you
Chemistry:
Solution for last week Part
10.
Part II: [16: (a) L (1).
Concentrated sulphuric acid has oxidising properties, which increase in power as the concent- ration of sulphur trioxide in- creases, Thus hot concentrated acid will oxidises sulphur to sulphur dioxide, while the acid itself is also reduced to sulph dioxide:
SO: →3502 2H20
(11) Sulphiaric acid in the con- centrated state has a great affinity for water. Organic comp ounds that contain the elements of water are easily dehydrated. For sugar, , action of concentrated acid will cause the formation of a spongy mass of carbon:
122201
120↓ + 118,0
(removed by conc
(111) Concentrated sulphuric acid like the dilute acid also process -es acidic properties. The acid, being dibasic will react with bases in two stages, forming firstly an acid salt, then with excess base to a neutral salt:
Zno+H SO
(b)
NaHSO+NaC1
Hydrogen chloride gas. NaCl + H SO
NaHSO HOL
Na 50+ HC1]
higher temperature required).
(11) Nitric acid vapour, the pour is coloured somwhat brown due to decomposition of nitric acid to nitrogen dioxide and oxygen.
BENO
BaHSO
+H2SO
NaNO
NaHSO HINO
Na SO+ HNO (higher
temperature. required).
(111) Carbon monoxide
HCOONa 30
HCOOH + NaHSO
as an
acid)
CO (coc. H2SO as
4
dehydrating agent)
(iv) Carbon monoxide and carbon
dioxides.
9202
10. Chlorine
Preparation:
H2C204 (H2SO4
2
acid).
NaHSO
aa an
CO2
HSO
conc.
as a dehydrat
b) from common sait:
Instead of using hydrochioric acid and manganese dioxide a mixture of salt, manganese dioxide, and sulphuric acid may be heated.
MnO 4NaCl + 48, 50
4NaHSO
MinCi
11) Instead of manganese dioxide, lead dioxide (Pb0) may be used
PbO2 + 4HC.
PbC1+ 28-0
0121
111) Red lead acts on concentrated
hydrochloric acid
8HC1
3PbC1
012
iv) Oxidation of concentrated
hydrochloric acid by potassium [permanganate.
No heat is required, and the facid can be added to the flask containing the permanganate by means of a dropping funnel.
+16HC1 →→2KC1 + 2MnC1
8H 0 + 501 ↑
By electrolysis of hydrochloric acid (conc.
Cathode of carbon or platinum Anode of carbon 2H01 At anode
Thin copper leaf also takes fire spontaneously:
Action on non-metals
Chlorine attacks all non-metals except carbon, oxygen and nitro- gen. The last three elements. combine with chlorine only in- directly.
a. White phosphorus, in a derlag- rating spoon, takes fire in chlorine, forming white clouas which are partly phosphorous trichloride (liquid) and phosphorus peutachloride(solid) 12P+ 3012
2PC1
2P
5012
Sulphur.
2PC15
When dry chlorine is passed over molten sulphur in a distilling flask connected to
a condenser, a reddish liquid distils over:
129
Sulphur monochloride
Priser opagising agent
Oxygen imparted to another substance Sulphites are oxidised to sulphates
HSO
H2O + Na2SO2
2HOT
2H01
Chlorine imparted to another substance Ferrous Chloride is oxidised to fermic chloride
2 FeCl + Cl
2FeC1
Hydrogen 18 oxidised to hydrogen chloride.
2H
201
2017 2e volume of chlorine liberated At Cathode: H ion discharge
012
H2 C12
2H + 2e
volume of hydrogen liberate, Properties Physical
Greenish yeaslow gas with punget smell, attack- ing mucous membrane, poisonous, diatomic molecules, soluble in water.
Chemical ---
ion of chiomne on nya roge Hydrogen elegant H2 C1-
ዘር
(Porus stehin
Tumes of. nyorogen
6. Compounds containing nyd roger react with chlorine, giving up their hydrogen to form nya rogen chloride
Waru turpentine,
8012 16H01
Candle wax
111) Ammonia
| 2NH
iv)
6H01
6HC1
3022 Hydrogen sulphide" HS
Cl
2. Action on metals
2H01
Chlorine attacks and directly. combines with all metala forma pa the highest chloride.
a. Sodium burns if heated 107
chlorine
21a
ga
ing agent ).
Mg
С12
1) 8) oxidation of concentrated.
hydrochloric acid by manganese dioxide
Mno
+ 4HC
MnCl2 2820
01.10
2NaC1
2401
Acid radical imparted to another substance
Ferrous sulphate oxidised ferric sulphate
2Feso
C12
Fe (S0) + 2HC1
Hydrogen taken from a substanc Hydrogen sulphide is oxidised to sulphur H2S + Cl2
2HC1
Chlorine Water or moist chlor- ine gas as an tleaching agent
· For bleaching action, chlorine first reacts with the water and forms hypochlorous zeid, HC10, this acid readily yield up its oxygen. It is this oxygen which causes the bleaching, the oxygen combines with the dye and forms a colourless compound material is bleached,
Cl2 + H2O
HC10+ Dye
hence the
ОТОН + ТОН
HC1 + (Dye + O
colourleas
The action is an oxidation of the dye
6. As a displacing element
Chlorine displaces bromine or iodine from solutions of potass= ium bromide or iodide.
2KBг + 012
2K1 + C12
2 KC1
2KC1
Br2 12
7. The action of chlorine on
Alkalis
a. Cold dilute sodium or potass->
ium hydroxide solution gives a mixture of chloride and hypochlorite
C12 + 2KOH
KC1 +
KC10
H2O
Magnesium burns in chlorine
b. Hot concentrated sodium or
potassium hydroxide solution gives a mixture of chloride and chlorate. 1301 6KON
► MgC12]
Zinc also burns in chlorine gas
ZaC1,
Tron or aluminium is beated chlorine
2PeC1
\270 + 3012
Ca(OH)2 Ca001
Manufacture of hydrochlore acid.:
2. Water purification, because
chlorine is a powerful killer
of
germs in the prevention or cholera, typhoid, etc. 3. As a bleaching agent, buc 19
too destructive to use in bleaching wool, silk, etc. 4. Manufacture of many organic compounds or chlorinat ed products, e.g. chlorogorm, D.D.T. carbon tetrachloride and synthetic rubber, synthal ic plastic and weed killer etc. Exercise Part 1
1. When chlorine is passed into solution sulphate and sulphuric acid, the salt undergoer
A. reduction
B. neutralisation)
C. oxidation
D. decomposition
E. double decomposition
2. Chlorine is usually added to pater which is going to be provid- ed in a town. This is in other to
dissolves the impurities in the water
precipitates all suspended matter in the water. softens the water
kill germs
E decolourise.it
3. Chlorine will turn moist blue litmus paper red. This is becaus chlorine water.
A. reduces litmus dye B: oxidises litmus dye
C. contains chloride ion
D. contains hypochlorous acid E. contains hydrochloric acid
4. The majority of chlorine used
industry is
A. Water purification
B. bleaching agent
C. manufacture of D.D.T.
D. manufacture of hydrochloric
acid.
manufacture of carbon tetrachloride
Chlorine is made commerically
rom
A. the action of mangenese
dioxide on sodium chloride and concentrated sulphuria acid
the action of mangenese “dioxide on concentrated/
hydrochloride acid
the oxidation of concentrated hydrochloric acid by sir, using a surface catelyst the electrolysis of dilute) hydrochlomo acid
the electrolysis of rused sodium chloride..
6. When chlorine is bubbled through a cold, dilute potassium hydroxide solution, the products formed are potassium chloride, water and
potassium hypochlorite potassium chlorate
R. potassium chloʻrite »
potassium perchlorate none of the above
Chlorine reacts directly, with, all non-metals except:
1. carbon
2. nitrogen
oxygen silicon
sul phu 17
which of the following aloernatīv
es is correct?.
P. 1, 2, and 3 only
Q.
R
S
A
and S only
* 53, and 4 only
2, 3, 4 only
none of these combination
8. When chlorine is passed into » cold dilute solütion of sod 1 um hydroxide it forma
P. perchlorate only
Q. chlorate only
R. chloride only
5KC1 + KC103
3.
+ 3H20
When chlorine is passed for a long time over solid slaked line, bleaching powder is formed.
a mixture of chlorate chloride q
1. a mixture of hypochlorite
"and chlorad s
(朱宪明日籤)
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