Topic 8 - Acids Flashcards Preview

Grace Chemistry IGCSE > Topic 8 - Acids > Flashcards

Flashcards in Topic 8 - Acids Deck (21)
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1
Q

Describe red litmus paper colour changes

A

Acid: red
Neutral: red
Alkali: blue

2
Q

Describe blue litmus paper colour changes

A

Acid: red
Neutral: blue
Alkali: blue

3
Q

Describe methyl orange colour changes

A

Acid: red
Neutral: yellow-orange
Alkali: yellow-orange

4
Q

Describe phenolphthalein colour changes

A

Acid: colourless
Neutral: colourless
Alkali: pink

5
Q

What is universal indicator used for

A

To approximate pH
It is a broad range indicator
Goes from red -> green -> blue

A combination of dyes

6
Q

What is an acid?

A

H+ donor (proton donor)

7
Q

What is an alkali

A

OH- donor

A soluble base

8
Q

What is a base

A

H+ acceptor (proton acceptor)
Metal oxide/hydroxide
Alkalis that are insoluble in water

9
Q

Describe the general formula for (dilute) acid + metal reactions

A

Acid + metal -> salt + H2

10
Q

What is a salt?

A

A compound formed when a hydrogen is displaced from an acid

An ionic compound formed during a neutralisation reaction

11
Q

Which metals are not reactive enough to react with an acid

A

Copper, silver and gold

12
Q

Which metals are too reactive to react with an acid

A

Potassium, sodium, lithium and calcium

13
Q

Describe the general formula for acid + base reactions

A

acid + base -> salt + water

14
Q

Describe the general formula for an acid + carbonate reaction

A

Acid + carbonate -> salt + water + carbon dioxide

15
Q

What is limewater?

A

Saturated calcium hydroxide solution

16
Q

How to prove the metal reactivity trend?

A

1) set up 3 boiling tubes and fill them with equal volumes of dilute HCl/H2SO4
2) place pieces of magnesium, zinc and iron into separate test tube (control size, shape, mass)
3) the speed of reaction is indicated by rate at which bubbles of hydrogen are given off
4) confirm the hydrogen with the squeaky pop test

17
Q

Describe the pH scale

A
0-3: strongly acidic 
4-6: weakly acidic 
7: neural 
8-10: weakly alkaline
10-14: strongly alkaline
18
Q

What is an indicator?

A

A dye which changes colour

19
Q

What colour is plain litmus in neutral solutions?

A

Purple

20
Q

Describe the equation for acid + base neutralisation

A

H+ (aq) -> OH- (aq) -> H2O (l)

The acid donates the protons which are accepted by the base. The products are always neutral.

21
Q

Describe the equation for acid + ammonia

A

Acid + ammonia -> ammonium salt

E.g: HNO3(aq) + NH3(aq) -> NH4NO3(aq)