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help!! plz

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~Dazzling Star~:

--- Quote from: Requiem on October 05, 2010, 06:15:22 pm ---Straight line graphs are the easiest part in IGCSE curricula and same is the case with acids and bases.
Just give us a few questions and you will get the idea when we solve them

--- End quote ---
ca u tell me the main things i should know abt in acids and bases??

Twinkle Charms:
I'd suggest u to go thru IGCSE Chemistry by B Earl & L D R Wilford. Everything is explained very clearly and in simple words.

elemis:

--- Quote from: ~Dazzling Star~ on October 05, 2010, 06:47:07 pm ---can i use any coordinates regarding x1 x y1 &y2??
and i donot understand what an intercept is could u explain again

--- End quote ---

If the two coordinates of a line are (1,2) and (6,5) then X1 = 1  X2 = 6  and Y1 = 2 and Y2=5.

You see the red line how it crosses the y axis ? The coordinates at which it crosses is given to be (0,7)

Therefore the y-intercept is 7.

Deadly_king:

--- Quote from: ~Dazzling Star~ on October 05, 2010, 06:48:46 pm ---ca u tell me the main things i should know abt in acids and bases??

--- End quote ---
ACIDS :
1. An acid is a substance that will produce hydrogen ions (H+) on dissolving in water.

There are two types of acids :
(i) Strong acid ---> Complete ionisation
(ii) Weak acid ---> Partial ionisation

Examples of strong acids are HCl and H2SO4 while all organic acids are weak acids.

Properties of acids :
1. An acid has a sour taste.
2. An acid will turn moist blue litmus paper red.
3. An acid will react with reactive metals to liberate hydrogen gas.
4. An acid will react with carbonates to liberate carbonates.

Tests for acids.
1. When moist blue litmus paper is brought into contact with an acid, there is a colour change from blue to red.
2.When solid sodium carbonate is brought into contact with the acid, there is effervescence and a gas carbon dioxide which turns lime water milky is liberated.

BASES :
1. An alkali or base is a substance that will produce hydroxide ions (OH-) on dissolving in water.

Properties of alkalis :
1. An alkali has a soapy feel.
2. An alkali will turn moist red litmus paper blue.
3. An alkali will react with an acid to form a salt and water.
4. An alkali when heated with an ammonium salt will liberate ammonia gas.

Test for alkali :
1. When moist red litmus paper is placed into a alkali, there is a colour change from red to blue.
2. When an alkali is heated with ammonium chloride, a gas ammonia that turns red litmus paper blue is liberated.

Deadly_king:
Oxides : There are four types of oxides.
1. A basic oxide is a metallic oxide that will react with an acid to form salt and water only.(Example :MgO)
Equation : MgO + 2HCl ----> MgCl2 + H2O

2. An acidic oxide is a non-metallic oxide that will combine with water to form an acid.(Example : SO3)
Equatio : SO3 + H2O ---> H2SO4

3. An amphoteric oxide is a metallic oxide that has both basic and acidic properties, that is it can behave as an acid as well as a base.(Example : PbO)
Equation : (i) PbO + 2HCl ----> PbCl2 + H2O
              (ii) PbO + Ca(OH)2 + H2O ----> Ca[Pb(OH)4]2

4. A neutral oxide is a non-metallic oxide that has neither basic nor acidic properties.(Example : CO2)

I guess that's all you need to know concerning oxides. :)

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