​CHEMISTRY OBJ

CHEMISTRY THEORY

1)

2a)

– Temporary hardness is caused by dissolved calcium hydrogencarbonate

– Permanent hardness is caused by dissolved calcium sulfate.

2bi) 

– Temporary Hardness can be Removed By Boiling

– Permanent hardness can be removed by … washing soda (sodium carbonate); ion exchange; the use of polyphosphate water softeners.

2bii) 

Advantages:

– Calcium ions in the water are good for children’s teeth and bones. 

– Some brewers prefer using hard water for making beer.

2biii) 

Disadvantages:

– It is more difficult to form a lather with soap.

– Scum may form in a reaction with soap, wasting the soap.

2ci)

A saturated solution is a chemical solution containing the maximum concentration of a solute dissolved in the solvent.

2ciii) 

– Anthracite Coal

– Bituminous coal

– Sub-bituminous coal

2civ) 

The anthracite coal: They are the purest forms of coal

2d) 

– Zinc is not a transition metal because it forms only Zn2+ ions with all the 3d electrons present.

– Zn not a transition metal, because it forms only Sc3+ ions with n d-electrons

2dii) 

Fine Chemicals: This is a chemical compound made in relatively small amounts and in a comparatively pure state.

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3ai)

petroleum gas and petrol->kerosene->diesel->asphalt

3aii)

I-asphalt

II-kerosene

III-petroleum gas and petrol

IV-asphalt

3bi)

i)ethene

ii)propene

3bii)

i)structural isomerism

ii)steveo isomerism

3biii)

19R-1s^2 2s^2 2P^6 3S^2 3P^6 4S^1

10S-1S^2 2S^2 2P^6

24T-1S^2 2S^2 2P^6 3S^2 3P^6 4S^2 3D^4

3biv)

group 6

3ci)

I- AgNO3(aq) and BaCl2

II-BaCl2 and Na2SO4

III-Ca(NO3)2 and H2CO3(aq)

3cii)

i)fitteration

ii)flocculation

iii)disinfection

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5a

i) increasing the surface area

By adding catalyst to the reaction

5iii)0.896dm^3 of CO2 was produced by 4g of caco3

5.    If 100g of caco3—–1mole of co2(22.4dm3)

4g——X

X=4*22.4/100

X=0.896dm3

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