Atmosphere and acids - 3.4

Question 1

what is an indicator?

Answer 1

an indicator is a substance that changes colour to tell you about the pH of a soluti9on

Question 2

what colours do methyl orange and phenolphthalein go when in different solutions?

Answer 2

methyl orange
- acidic colour = red
- neutral colour = yellow
- alkaline colour = yellow

phenolphthalein
- acid colour = colourless
- neutral colour = colourless
- alkaline colour = pink

Question 3

what colours do red and blue litmus paper go when in different solutions?

Answer 3

red litmus
- acidic colour = red
- neutral colour = red
- alkaline colour = blue

blue litmus
- acidic colour = red
- neutral colour = blue
- alkaline colour = blue

Question 4

what are the four gases air is mostly composed of?

Answer 4

nitrogen - 78%
oxygen - 21%
argon - 0.96%
carbon dioxide - 0.04%

Question 5

what is element combustion?

Answer 5

when an element reacts with oxygen to produce an oxide

Question 6

what are the three important combustions?

Answer 6

1 - Magnesium
magnesium + oxygen –> magnesium oxide
2 - Sulphur
sulphur + oxygen –> sulphur dioxide
3 - Hydrogen
hydrogen + oxygen –> hydrogen oxide (water)

Question 7

what is iron(II)?

Answer 7

Fe 2+

Question 8

what is silver?

Answer 8

Ag +

Question 9

what is iron(III)?

Answer 9

Fe 3+

Question 10

what is zinc?

Answer 10

Zn 2+

Question 11

what is copper?

Answer 11

Cu 2+

Question 12

what is lead?

Answer 12

Pb 2+

Question 13

what is the chemical test for oxygen?

Answer 13

glowing splint –> relights
This is because the oxygen allows the wood in the splint to combust more efficiently

Question 14

What happens if they dissolve in water?

Answer 14

oxides tend to form a acid or alkaline solution depending on whether the original element was metal or non-metal

metal –> alkaline solution
non-metal –> acid solution

Question 15

how can you determine if an unknown element was metal or non-metal?

Answer 15

• combust it in oxygen
• dissolve the oxide formed
• check the pH of the solution with an indicator

Question 16

What is an acid?

Answer 16

H+ donor

Question 17

What is a base?

Answer 17

H+ acceptor

Question 18

What is an alkali?

Answer 18

OH- donor

Question 19

What is the formula for Hydrochloric acid?

Answer 19

HCl

Question 20

What is the formula for Nitric acid?

Answer 20

HNO3

Question 21

What is the formula for Sulphuric acid?

Answer 21

H2SO4

Question 22

What is the formula for Phosphoric acid?

Answer 22

H3PO4

Question 23

What is the formula for Carbonic acid?

Answer 23

H2CO3

Question 24

What is the formula for Sodium hydroxide?

Answer 24

NaOH

Question 25

What is the formula for Potassium hydroxide?

Answer 25

KOH

Question 26

What is the formula for Ammonium hydroxide?

Answer 26

NH4OH

Question 27

What is the formula for Ammonia?

Answer 27

NH3

Question 28

What are polyatomic ions?

Answer 28

A polyatomic ion is an ion that contains more than one atom

Question 29

What happens when bases react with metals?

Answer 29

They form a salt and water

Question 30

What is an important observation that is made when an acid and base reacts?

Answer 30

The base disappears because it is used up in the reaction.

Question 31

Making Salt Crystals:

Answer 31

1. add excess base to hot acid - this makes the salt solution quickly and ensures all the acid is used up 2. filter out excess base - the salt solution is the filtrate and is collected in an evaporating basin 3. heat the salt solution until crystals start to form around the edges - this saturates the solution so that crystals form most efficiently 4. leave the salt solution to crystallise - evaporation of water allows crystals to form

Question 32

Making pure, dry crystals of a soluble salt:

Answer 32

1. First, you make the salt solution a. The insoluble base method b. The titration method 2. Second, you crystallise the salt - This is done in the same way, regardless of the method you use to make the salt solution

Question 33

The insoluble base method:

Answer 33

1. Heat the acid - hot acid has more energy so it reacts faster with the base 2. While stirring, add base until no more will dissolve - This guarantees the base is in excess so that we know all the acid has been used up 3. Filter out the excess base

Question 34

The titration method

Answer 34

1. Perform a titration to measure the volumes of acid and alkali that neutralise each other 2. Repeat the titration, but this time: a. don't put the indicator in b. use the burette to add exactly the right volume for neutralisation Now the salt solution is made you perform crystallisation to get pure, dry salt crystals

Question 35

What happens when carbonates react with metals?

Answer 35

They from a salt, water and carbon dioxide

Question 36

What are the two important observations in an acid and carbonate reaction?

Answer 36

- The carbonate disappears This is because it is used up in the reaction - There is fizzing This is because a gas(carbon dioxide) is produced

Question 37

What is the chemical test for carbon dioxide?

Answer 37

Bubble into limewater --> goes cloudy This is because CO2 reacts with the limewater to make an insoluble white solid

Question 38

What is precipitates

Answer 38

A precipitate(ppt) is an insoluble solid that forms inside a solution.

Question 39

How can you tell if precipitate will form by mixing ions up and seeing if either of the resulting compounds are insoluble?

Answer 39

If an insoluble compound is formed, it will appear as a precipitate.

Question 40

Making salts by precipitation:

Answer 40

mix solutions together filter out the solid precipitate wash - by rinsing under water method of drying - pat dry with filter paper