1974-03-20 — Page 21

化交育:草一幕張六第4日 七十月二年寅甲愿夏 WAH KIU YAT PO

XXX

凱

恒

【 1874 中學會考試題預習專欄

堅道書院主機

The as is collected over water

Frogen dioxide N-0, or NO2

This oxide is a greenish-yellow liquid boiling at 22 c. "At temperatures just above. the boling point, the gas has the formula N2Oy. As the temperature:

israised it decomposes, first into molecules of formula No and

then into: nitric oxide:ahd axygen-the reverse reactions. occurring on cooling: :

報日僑筆

1. On the surface or a catalyst, about 500°c., ammonia is oxidized. by the oxygen in air to nitric oxide,NO. (The catalyst is metal11 Kanze made of platinum or a rhodiu platinum alloy.

4 NK

6H

3. The nitric oxide, after cooling is oxidized by the oxygen in air ffo. nitrogen dioxide, NO. which is

also a' gas:

2NO

三期星

Dilute nitric acid as, an acid:

It turng 11tmüs red.

日十二月三年四七九一藤公年三十六國民拳中

1974中學會考試題預習專欄

The Locus of a point is the paths

It will react with bases to gi a salt and water:

traced out by a point which moves der certain conditiona...

NaOH + HNO2

NaNO + H20-

3. Magnesium is the only metal

which when reacts with very dil nitric acid, will give hydrogen Mc+ ZN03 YOU NO2) 1⁄2 *; H2

4. It will react with carbónate ti

give carbon dioxide:

數學科(乙)

文長波

In analytical zoometry, if we

Assume that the point on the locus is P(x,y), then the given condition will lead to an equation involving tae variables x and y called the equation of the focus

hataematics (19)

"Solution to exercise if

1. Let B(x,y) bu the image.

în tue line x+y-7=Q..

Examule 1

The mid- of the line joining to (1,2) lies the line 2x+3y=5• ̈ Find the equation of hig Ret P

371ation: Det P(x,y)

the loci,

any point on

the or-ordinates of M are

化學科(乙)(牛八)

CHEMISTRY (18)

Suggested answers for last week: 1.(1) When ammonia is passed over

hot copper oxide is reduced to metal, and the gas is oxidized to iltrogen and water.

30u0

** (11) "Aumonia gas does not burn in air but burns in oxygen with. greenish-yellow. flame; forming nitrogen and water.

(ii) Ammonia gas reacts direct ly with hydrogen chloride forming: salt. When these two gases are. brought together, white. funes are produced due to the formation of: minute particles of ammonium. chloride.

NH + HOL

NH, CL

(iv) Ammonia gas can react with: carbon dioxide in the presence of water, forming a salt, ammonium carbonate

2NH CO

2.(a)When ammondun hydroxide is

first added, a pale-blue gelatini ous precipitate is formed,But when ammonium hydroxide 1s added in excess, the precipitate disap- pears, vand the solution: becomes. deep blue in colour.. When the ammonium hydroxide Le added to the copper sulphate solution, a pale-blue gelatinous precipitate coppar hydroxide is formed:

CUSO + 2NH OF

But when ammonium hydroxide. ta. added in excess, the copper hydre oxide forms a complex 1on with ammonium hydroxide. The product (cuprammonium hydroxide) so formed 18 soluble and 18 deep blue in colour, constituting the deep blue colour of the liquid. Cu(OH)2+4NH, OH:

> Cu(NH) (OH)2

+480

(b).By the apparatus as shown in the diagram, nitrogen cam be prepared: by :passing dry.amonia. over, hot copper'oxide,

NHS

+3cup

+3Cu 3H

The gas collected over water in. the Jar is inertf it has no react. ion with glowing splint, litmus, and Iime-water, It is nitrogen.. This vexperiment proves that ammonia contains nitrogen,

The oxides of nitrogen

1. Nitric oxide NO

Nitric oxide is usually prepared in the laboratory by reducing nitric acid (of atrength. 1 part acid. tod of water) by copper:

3Cu(NO3)2 + 2N

4H20

3Cu + 8HNOㄢ

dissociation 2NO

20

yellow brown

association · ·

It is along with. oxygenby heat: ing any nitrate other than those of sodium, potassium and armordun In the Laboratory, lead nitrate. is usually used andthe nitrogen- dioxide separated from the oxy- gen by passing the gases:throgh a freezing" mixture of ice and salt:

2Pb(NO3)2

Comparison of prop ties of the oxides of nitro

Nitric Oxide

a.Colouriesp

b.Insoluble

water

3. The nitrogen dioxide is dis- solved in water with which Lt. react to form nitric acid:

3NO + H2O

RHNO3

NO

The nitric oxide that is formed in this last reaction is used again in stage 22:

|Properties::

Nitrates:

A.: Preparation

1) By the action of nitric acid

on bases, e.g. NaOH,KON, OH

NaOH +

1) By the action of nitric on.

̇most metals, e.gcuPBASER

(iii) By the action of nitric acti

on carbonates,.g. Ca, 5, 40,

·PhCO3+8

B+2HNO + Fb(NO3)2+H2O+Cl

Nitric acid is a heavy, colourless 1iquid, miscible with water in all proportions, pungent smell; corros ive action on flesh, clathes; wood B. etc. Boling point 30.; specific gravity 1.53. Ordinary *Concentrate nitric acid contains about 70% HNC Conc. nitric acid decomposes slowl in light and on heating:

Nitrogen dioxide 4 HNO3

Brown:

Soluble, giving HNO2 and NO,

e.Support the combustion of those

substances giving out sufficient heat. to decompose the gas into :: nitrogen and oxygen; then the burning substance burns more bri ly than in air, since each gas 'contains a higher proportion df

oxygen than does air;

and the nitrogen dioxide so formed accounts for the yellow or brown. colour of the concentrated acid. Concu nitric acid is a powerful | oxidizing agent:

Conc. nitric is an accepter of electrons, ear!

从HNOg

cone.

SANO3

d. With air turns No action in air For examples:

-crown_forming

nitrogen diduide 200+0

2N0.

Ji). On, metals

2N0

CuCNC + ZN03 2 3Cu+ •HNQz →3Cu(N©zλ2+482C+€N° All are reduced, to nitrogen wher passed over many heated metaisic. 4Zn+104NOz - 4Zn(NO3), +3H2O*N£ †

20 +20u

2000+ N2

4ZMCNT)2+5H_0 F.with cold ferrous Brown colorati 4Zn+105NO,

sulphate solution, due to NO form brown coloration when the gas

reacts with wat

Nitric acid,HNOZ Lab. Preparation:

Sodium or potassium nitrate is heated with conc. aulphuric acid

in a glass retort. The nitric aci is given off as a gas and is condensed in a water cooled flask With excess of potassium nitrate and higher temperature, potassium sulphate is formed; but this temp: may crack the glass and decompose some ofthe acid:

Industrial method:::

Much of the nitric acid for indust ry is made from ammonia by Ostwalc

Process. This has three steps, as

follows:

On non-metals

Carbon is oxidized to CO by hot and.cone. HNO3

C+ 4HNO

20

dil.

Sulphur is oxidized to hot HNO3 56:

AHNOL

dil

35

Cm compounds.

-Ferrous salts'are oxidized to

ic sal

Hydrogen sulphide is oxidizes yellow ppt. of sulphur.

280

Sulphur dioxide is, oxidized to

sulphuric acid:

2 NO

Properties:

All nitrates are soluble in water and react with hot conc, sulphuric acid to form nitric : vapour.,Many nitrates: are also

deliquescent.

Uses of potassium and ammonium: nitrates:.

̇Potassium nitrate is not deliqu

escent. So, it is used in the manufacture of explosives, such as Wun-powder, which contains: roughly by weight,

l part of charcoal; part of sulphur 6 parts of potassium nitrate.

Ammonium. nitrate used in many explosices, such as amponal (a mixture of ammonium nitrate and aluminium powder)When it 18-

40410_+6日_O+ON

Again a large volume of hot gas is produced from a small volume: of explosive. The other uses of ̇ammonium: nitrate as a fertilie in nitrochalk (a miture of ammonium nitrate and powder chalk).

Tests for nitrates:. -1. Brown Ring test.

Dissolve the suspected nitrate ii. water and add a fresh solut: ion of ferrous sulphate, shake * well. Incline the test-tube

and slowly pour cone, sulphurdc acid down the inside of the tube so that it form a Tayer below the level of the aqueous solution A brown ring (FeSO, NCY forms at the junction oft the twd layers of liquid if a nitrate is present..

2. The cópper test:

Add a piece of copper to the aolid suspected nitrate; 'and add conc. sulphuric acid heat gently. If a nitrate is present the brown fumes. of nitrogen dioxide will be given off.

Question for. this week;

Describe: how..you would ahoy. by experiment the presence of Oxygen in nitric acid.

Describe how you would perform the brown ring test on a sample of sodium nitrate and explain the che the chemical reactions involved

3. How would you prepare crystal-

line specimens'of sodium nitrd and lead nitrate from a mixture 'of sodium carbonate and lead

carbonate?

Compare the action of heat on

these two nitrates.

X=4

(1)+(2)←2x=8

(2)=(1.)>2y=10

The co-ordinstes of the ina- ge of the point (2,3). in the Line:x+y-7md are (4,5).

Equation of the line" passing through (-49-1) 20

8x-3y+23=0;

alope

Equation of the red straight line-

2x-10-3y-21 2-3y+11=0

slope of 3x+1.2y

Equation of the re straight line is

4x-20-y-7 4x-13=0

tan

can on tan (180

-tan B. →2

Equation of the required straight line is:

-2x+10=y-7

17-0

lies on 2(x+1)+ 2x+2+3y+610 1.8. 2x+3x-2=0 The equation of the

2x+3y-2=0

Example 2 à straight line cuts the

nampak 2 dB and AB 20units. Find the locus the mid-pt of A3,

Exam

Let:2\x,3} be any point .or the loci,

品

The co-ordinates of A and B are^(2x,0) and (0,2y): reapectively.

AB = 20.

2:400 100

The Joeye of the as 100

Find the equation" of the circle on the dameter " whose enda are (-3,-2) ang (2,5)*

Solution: Let P(x,y) be any point

the circle

APB

33-14

The equation of circle

Exercise 19

A line parallel to the y-axis meets the curvey=3xs at R and the line y=x+1 at Si

Find the locus of the mid-point of RS,

2. A is a variable point on the x-

-axis and B is the point (1,3)..

A line through B perpendicular to A3, meets the y-axis at·0. Perpendiculare to the axis at A. and C meet at P. Find the locus

of the point P?

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在大會堂高座八樓 老畫師到醴平“展

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昨起舉行四天廿四孝圖最名貴

劇歌王師先子孔

|港劇藝學會主辦

|師望亮。二〇獣

初,四月一日起

容可度今晚演唱的

四及當期樂節率

晚四打三心理障

四道七月一

克鎮二六號九横版

廿六日展出大會堂八

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續寬

續講楞嚴經撮要

寬如寬榮兩法師

·基粗生波已伏,此

↗乃頭識定境

時。上之内守閒

現」非分別色相之

佛德似绣似物,於

·別都無之境,仂仿

·能分別之心,所分 分別不當J,有一

·文句古澤作都無 無可分別放(因此一

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,置空嫩白亦願非彈一也爲六

非一無色五都非。都較 卽阗非以,根無色

無餘

,以非實,對杯

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三乘班人所證之真

高空,此非色非空

梯式:

可口可辣,空液

智者。見外五非心,所得伏關

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非淼過若眞萜故廣之即是 境名有此德

子子關

宗

油藏境比乃爾:境鯽境生精下空有

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·濕別識不絕 中药守注

開故明 在無 外明所守幽之

為覺云 了取 獨分 絲了守附

法知一同獨 散別,不,開之。,可非微去,色

座內縦五影位,當行五 境比 是對 色细 佩如非

*量約。齲湖者

其中

中有云,有

四:月

晚四份

班

·希穎爲予作雙溪別館國賦謝

余少

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錢後,洋並,作能

山

中腳病理

如何

勞。

飛草行

鄉