C5 - Chemical Change Flashcards
What is Titration?
where a solution of known concentration is used to determine the concentration of an unknown solution
What is the formula triangle for concentration, number of moles and volume?
Number of moles
—————————-
Concentration X Volume
What is the equation to convert a concentration in mol/dm°3 into g/dm°3?
Mass in grams = moles x relative formula mass
What does the pH scale go from?
0 to 14
What does a lower pH of a solution mean?
More acidic
What does a higher pH of a solution mean?
More alkaline
What pH does a neutral substance have?
7
What is an example of a nuetral substance with a pH of 7?
Pure water
What is an acid?
A substance that forms aqueous solutions with a pH of less than 7
What is a base?
A substance with a pH greater than 7
What is an alkali?
A base that dissolves in water to form a solution
What is neutralisation?
The reaction between acids and bases
What do alkalis form in water?
OH- ions
What does an acid + a base form?
Acid + base ——> salt + water
What is pH just a measure of?
How acidic or alkaline a solution is
What is pH just a measure of?
How acidic or alkaline a solution is
How can you measure pH?
Using Universal/Single indicators
What is the benefit of the pH probe compared to the indicators when meauring pH?
More accurate and precise as doesnt require human judgement
What is the benefit of the pH probe compared to the indicators when meauring pH?
More accurate and precise as doesnt require human judgement
What do neutralisation reactions always produce?
Salt and water
What pH would a neutralisation reaction produce?
A neutral pH of 7
What are the 3 common acids? And what are their formulas?
Hydrochloric acid (HCl)
Sulfuric acid (H2SO4)
Nitric acid (HNO3)
What are the 2 common bases? And what are their formulas?
Sodium hydroxide (NaOH)
Calcium carbonate (CaCO3)
What makes an acid strong?
If the ionise completely
What does the term ‘ionise completely’ when talking about strong acids?
The reactants turn completely into products
As the concentration of hydrogen ions gets higher, the pH gets _______
Lower
Does a low pH have a high or low concentration of hydrogen ions?
High
What is the product of an acid + a metal carbonate?
Salt + water + CO2
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
- Pour 25cm cubed of dilute hydrochloric acid into a beaker and gently heat it up with a bunsen burner safety flame
- Gradually add the zinc carbonate until it no longer disappears and is in excess
- Filter the solution to remove excess Zinc carbonate
- Heat the solution again in a water bath until crystallisation occurs
- Pat the crystals of Zinc Chloride with paper to dry and Leave them to further crystallise
Explain how you would carry out the making of soluble salts using an insoluble base experiment?
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
In the making soluble salts using an insoluble base experiment, what does it mean when the base is no longer dissapearing?
All of the acid has been neutralised
When we talk about the reactivity of a metal, what does it mean in terms of ions?
How easily it forms positive ions (loses electrons)
What is oxidation?
The process of gaining oxygen
What is reduction?
The loss of oxygen
What do relative reactions of metals with water produce?
A metal hydroxide and hydrogen gas
What does OIL RIG stand for?
Oxidation is loss (of electrons)
Reduction is gain (of electrons)
Metal oxides
Metal hydroxides
Metal carbonates.
What do they have in common?
They are all neutralisation reactions
What are the products when a metal oxide and an acid react?
Salt + water
What are the products when a metal hyroxide and an acid react?
Salt + water
When we say a metal forms positive ions?
It loses its electron(s) and becomes positive
“Pretty Silly Lions Catch Many Clever Zebras In Huge Cuages”
Potassium
Sodium
Lithium
Calcium
Magnesium
Carbon
Zinc
Iron
Hydrogen
Copper
More reactive metals can _________ less reactive metals
Displace
If you put magnesium into a solution of Iron Sulfate, what will the products be and why?
MAGNESIUM would displace the IRON to form MAGNESIUM SULFATE
because Mg is more reactive than Fe
How do you extract metal from metal oxides?
React the metal oxide with carbon. The carbon will take the oxygen to form CO2
You will now have metal + CO2
When you extract metal from metal oxides, using carbon, your products will be metal + CO2
What has reduced and what has become oxidised
The metal oxide has been reduced (to form metal)
The Carbon has been oxidised (to form CO2)
What is the other way you could extract metal from metal oxides that is really expensive? (without using carbon)
Electrolysis
Show the redox half equation for Ca.
Ca2+ + 2e- ——> Ca
Explain how you would carry out a titration experiment.
- Use a pipette to transfer 25cm3 of sodium hydroxide into a clonical flask
- Add 5 drops of indicator like methyl orange
- Place onto a white tile to see the colour change clearly
- Fill a burette with sulfuric acid
- Slowly add the acid to the solution (while swirling) until it is neutralised
What is the product of hydrogen + hydroxide?
Water
Hydrogen reacts with hydroxide to produce water?
What is the symbol equation for this?
H+ + OH- —–» H2O
What is the purpose of a Titration experiment?
To determine the concentration of an unknown solution
Why are Universal Indicators used for titrations?
To estimate the pH of a solution by examining colour change
Why would you use single indicators for titration?
You want to see a sudden colour change
Name two other substances that can each be reacted with a dilute acid to make
zinc chloride
Zinc
Zinc Oxide
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.
Methyl orange
Orange to yellow
