C5 - Chemical Change

Question 1

What is Titration?

Answer 1

where a solution of known concentration is used to determine the concentration of an unknown solution

Question 2

What is the formula triangle for concentration, number of moles and volume?

Answer 2

Number of moles
—————————-
Concentration X Volume

Question 3

What is the equation to convert a concentration in mol/dm°3 into g/dm°3?

Answer 3

Mass in grams = moles x relative formula mass

Question 4

What does the pH scale go from?

Answer 4

0 to 14

Question 5

What does a lower pH of a solution mean?

Answer 5

More acidic

Question 6

What does a higher pH of a solution mean?

Answer 6

More alkaline

Question 7

What pH does a neutral substance have?

Answer 7

7

Question 8

What is an example of a nuetral substance with a pH of 7?

Answer 8

Pure water

Question 9

What is an acid?

Answer 9

A substance that produces H+ ions when dissolved in water

Question 10

What is a base?

Answer 10

A substance with a pH greater than 7

Question 11

What is an alkali?

Answer 11

A base that dissolves in water to form OH- ions

Question 12

What is neutralisation?

Answer 12

The reaction between acids and bases

Question 13

What do alkalis form in water?

Answer 13

OH- ions

Question 14

What does an acid + a base form?

Answer 14

Acid + base ——> salt + water

Question 15

What is pH just a measure of?

Answer 15

How acidic or alkaline a solution is

Question 16

What is pH just a measure of?

Answer 16

How acidic or alkaline a solution is

Question 17

How can you measure pH?

Answer 17

Using Universal/Single indicators

Question 18

What is the benefit of the pH probe compared to the indicators when meauring pH?

Answer 18

More accurate and precise as doesnt require human judgement

Question 19

What is the benefit of the pH probe compared to the indicators when meauring pH?

Answer 19

More accurate and precise as doesnt require human judgement

Question 20

What do neutralisation reactions always produce?

Answer 20

Salt and water

Question 21

What pH would a neutralisation reaction produce?

Answer 21

A neutral pH of 7

Question 22

What are the 3 common acids? And what are their formulas?

Answer 22

Hydrochloric acid (HCl)
Sulfuric acid (H2SO4)
Nitric acid (HNO3)

Question 23

What are the 2 common bases? And what are their formulas?

Answer 23

Sodium hydroxide (NaOH)
Calcium carbonate (CaCO3)

Question 24

What makes an acid strong?

Answer 24

If they ionise completely in aqueous solutions

Question 25

What does the term 'ionise completely' when talking about strong acids?

Answer 25

The reactants turn completely into products

Question 26

As the concentration of hydrogen ions gets higher, the pH gets _______

Answer 26

Lower

Question 27

Does a low pH have a high or low concentration of hydrogen ions?

Answer 27

High

Question 28

What is the product of an acid + a metal carbonate?

Answer 28

Salt + water + CO2

Question 29

This question is about making a soluble salt. Plan a method to make pure, dry crystals of zinc chloride from zinc carbonate and a dilute acid

Answer 29

1. Pour 25cm cubed of dilute hydrochloric acid into a beaker and gently heat it up with a bunsen burner safety flame 2. Gradually add the zinc carbonate until it no longer disappears and is in excess 3. Filter the solution to remove excess Zinc carbonate 4. Heat the solution again in a water bath until crystallisation occurs 5. Pat the crystals of Zinc Chloride with paper to dry and Leave them to further crystallise

Question 30

Explain how you would carry out the making of soluble salts using an insoluble base experiment? Skip this we have a better 1

Answer 30

Place dilute HCL acid into a beaker and gently heat with a bunsen burner Then keep adding an insoluble base a bit at a time until the base no longer disappears

Question 31

In the making soluble salts using an insoluble base experiment, what does it mean when the base is no longer dissapearing?

Answer 31

All of the acid has been neutralised

Question 32

When we talk about the reactivity of a metal, what does it mean in terms of ions?

Answer 32

How easily it forms positive ions (loses electrons)

Question 33

What is oxidation?

Answer 33

The process of gaining oxygen and losing electrons

Question 34

What is reduction?

Answer 34

The loss of oxygen and gain of electrons

Question 35

What do relative reactions of metals with water produce?

Answer 35

A metal hydroxide and hydrogen gas

Question 36

What does OIL RIG stand for?

Answer 36

Oxidation is loss (of electrons) Reduction is gain (of electrons)

Question 37

Metal oxides Metal hydroxides Metal carbonates. What do they have in common?

Answer 37

They are all bases that react with acids in neutralisation reactions

Question 38

What are the products when a metal oxide and an acid react?

Answer 38

Salt + water

Question 39

What are the products when a metal hyroxide and an acid react?

Answer 39

Salt + water

Question 40

What do we mean when we say a metal forms positive ions?

Answer 40

It loses its electron(s) and becomes positive

Question 41

"Proud Strong Lions Catch Many Clever Zebras In Huge Cuages"

Answer 41

Potassium Sodium Lithium Calcium Magnesium Carbon Zinc Iron Hydrogen Copper

Question 42

More reactive metals can _________ less reactive metals

Answer 42

Displace

Question 43

If you put magnesium into a solution of Iron Sulfate, what will the products be and why?

Answer 43

MAGNESIUM would displace the IRON to form MAGNESIUM SULFATE because Mg is more reactive than Fe

Question 44

How do you extract metal from metal oxides?

Answer 44

React the metal oxide with carbon. The carbon will take the oxygen to form CO2 You will now have metal + CO2

Question 45

When you extract metal from metal oxides, using carbon, your products will be metal + CO2 What has reduced and what has become oxidised

Answer 45

The metal oxide has been reduced (to form metal) The Carbon has been oxidised (to form CO2)

Question 46

What is the other way you could extract metal from metal oxides that is really expensive? (without using carbon)

Answer 46

Electrolysis

Question 47

Show the redox half equation for Ca.

Answer 47

Ca2+ + 2e- ------> Ca

Question 48

Explain how you would carry out a titration experiment.

Answer 48

1. Use a pipette to transfer 25cm3 of sodium hydroxide into a clonical flask 2. Add 5 drops of indicator like methyl orange 3. Place onto a white tile to see the colour change clearly 4. Fill a burette with sulfuric acid 5. Slowly add the acid to the solution (while swirling) until it is neutralised

Question 49

What is the product of hydrogen + hydroxide?

Answer 49

Water

Question 50

Hydrogen reacts with hydroxide to produce water? What is the symbol equation for this?

Answer 50

H+ + OH- ----->> H2O

Question 51

What is the purpose of a Titration experiment?

Answer 51

To determine the concentration of an unknown solution by reacting it with a solution with a known concentration

Question 52

Why are Universal Indicators used for titrations?

Answer 52

To estimate the pH of a solution by examining colour change

Question 53

Why would you use single indicators for titration?

Answer 53

You want to see a sudden colour change

Question 54

Name two other substances that can each be reacted with a dilute acid to make zinc chloride

Answer 54

Zinc Zinc Oxide

Question 55

Name an indicator that can be used in this titration. Give the colour change of the indicator when acid from a burette is added to the alkali in the flask.

Answer 55

Methyl orange Red to yellow