Topic 4 Using Spec

Question 1

What are acids in terms of ions

Answer 1

Substances that form hydrogen ions when dissolved in water

Question 2

What are alkalis in terms of ions

Answer 2

Substances that form hydroxide ions when dissolved in water

Type of base

Question 3

On the ph scale describe acids alkalis and water

Answer 3

Neutral is 7 which is water and it’s what acids and alkalis combine to form
Acidic solutions have a lower pH
Alkaline solutions have a higher pH

Question 4

Describe the effect of high concentration of hydrogen ions In an acidic solution

Answer 4

Higher the concentration of hydrogen ions in an acidic solution the lower the pH

Question 5

Describe the effect of high concentration of hydroxide ions In an alkaline solution

Answer 5

The higher the concentration of hydroxide ions in an alkaline solution, the higher the pH

Question 6

What are the three types of indicators

Answer 6

Methyl orange
Phenolphthalein
Litmus paper

Question 7

What colour does methyl orange go

Answer 7

Red in acid

Yellow in alkali

Question 8

What colour does phenolphthalein go

Answer 8

Colourless in acid

Pink in alkali

Question 9

What colour does litmus paper go

Answer 9

Red in acid

Blue in alkali

Question 10

Measuring change in pH practical

Answer 10

Measure out mass of a base onto a piece of paper
Add powdered calcium hydroxide into the beaker of a fixed volume of dilute hydrochloric acid
Stir and then estimate and record the pH of the mixture
Repeat until a maximum pH 14

Question 11

How could you improve this practical

Answer 11

Use a pH probe date logger so u don’t have to judge the colour of each value of pH

Question 12

What is the independent and dependent variable

Answer 12

Independence-Amount of base added

Dependant - pH of liquid

Question 13

What does the term ‘concentrated’ mean

Answer 13

Concentrated solution contains a relatively large amount of the solute in the same volume of solvent

Question 14

What does dilute mean

Answer 14

A dilute solution contains a relatively small amount of the solute in a given volume of solvent.

Question 15

How can acids be neutralised

Answer 15

By reacting with a base

Question 16

General reaction of metal hydroxides

Answer 16

Acid + hydroxide -> salt + water

Eg hydrochloric acid + sodium hydroxide-> sodium chloride + water

Question 17

General reaction for metal carbonates

Answer 17

Acid + carbonate-> salt + water + carbon dioxide

Question 18

General reaction for metal oxides

Answer 18

Acid + oxide -> salt + water

Question 19

Describe the test for hydrogen

Answer 19

Place a lit splint close to the mouth of a test tube that contains a gas.
If the gas is hydrogen, a “squeaky pop” sound will be produced.

Question 20

Describe the test for carbon dioxide

Answer 20

Take an aqueous solution of limewater (calcium hydroxide) and bubble through the gas.
If the gas is carbon dioxide, the limewater solution will turn from clear to cloudy.

Question 21

What is the product of a neutralisation reaction

Answer 21

Water

Question 22

How do acids and alkalis react to form water

Answer 22

They go through a neutralisation reaction where the hydrogen ions react with the hydroxide ions

Question 23

If soluble salts are prepared from an acid and an insoluble reactant explain why excess of the reactant is added

Answer 23

To make sure all of the acid has reacted
This is done by filtering, filtering removes the unreacted insoluble reactant from the salt solution so that only salt and water remains

Question 24

If soluble salts are prepared from an acid and an insoluble reactant explain why excess of the reactant is removed

Answer 24

To remove impurities from the salt that has been prepared

Question 25

If soluble salts are prepared from an acid and an insoluble reactant explain why the solution remaining is only salt and water

Answer 25

Because you have reacted all the acid and removed all the impurities

Question 26

Explain why if soluble salts are prepared from an acid and a soluble reactant, why titration must be used

Answer 26

Because there is no insoluble excess reactant that could be removed by filtration

Question 27

Explain why if soluble salts are prepared from an acid and a soluble reactant why the acid and soluble reactants are mixed in the correct proportions

Answer 27

As we want a precise amount of the salt and no excess acid or any of the other reactants

Question 28

How are blue copper sulfate crystals formed

Answer 28

by adding black copper oxide to sulfuric acid

Question 29

Practical for producing pure dry sample of a double salt

Answer 29

Use a Bunsen burner to warm the acid and then add the insoluble solid Filter the solution to remove excess insoluble solid Heat the solution in an evaporating basin above a beaker of water (water baths ensure gentle heating) Allow solution to cool and more water to evaporate As water evaporates solution will become more concentrated and salt will begin to crystallise

Question 30

Acid-alkali titration practical

Answer 30

Using pipette add set volume of strong alkali to a conical flask and add few drops of indicator Place strong acid of known concentration in a burette Gradually add the acid to the alkali and as you get closer to end point start to add the acid at a slower rate As soon as indicator changes colour, stop adding acid

Question 31

What are we trying to work out in a titration experiment

Answer 31

Volume of acid needed to neutralise the alkali

Question 32

What common salts are soluble

Answer 32

Sodium , potassium and ammonium

Question 33

What chlorides aren’t soluble

Answer 33

Silver and lead

Question 34

What sulfates aren’t soluble

Answer 34

Lead , barium, calcium

Question 35

Potassium sulfate solution is mixed with barium chloride solution. Predict whether a precipitate will be formed and name it

Answer 35

barium sulfate will be formed as barium is insoluble