Chemical changes Flashcards by Rayan Pesnani

What does the pH scale range from

0-14

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Where are Acids and Alkalis on the pH scale

0-6.9 is acids
7 is neutral
7.1- 14 is alkalines

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What can be used to measure the pH of a solution

An indicator like universal indicator that shows colours like the rainbow

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What ions do acids and alkalines form

Acids- H+ ions
Alkaline- OH- ions

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What is an acid

A substance that forms aqeous solution with a pH less than 7. Acids form H+ ions in water

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What is a base

A substance with a pH over 7

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What is an alkali

A substance that forms aqeous solution with a pH more than 7. Acids form OH- ions in water

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What is the reaction between acids and bases called

Neutralisation

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Give the generic formula of neutralisation reaction

Acid + Base –> Salt + Water

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What is a strong acid and give an example

An acid that fully ionises an aqeous solution and all acid particles dissociate to release H+ ions
Example: HCl

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What is a weak acid and give an example

An acid that only partially ionises in an aqeous solution and only a small proportion of acid particles dissociate to form H+ ions
Example: Ch3COOH- Ethanoic acid

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Are strong or weak acids reversible

You can reverse weak acids dissociating by reacting it with other things.

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What relates H+ ions and rate of reactions and how do strong and weak acids’ reactivities compare

If concentration of H+ ions is higher, the rate of reaction will be faster so strong acids will be more reactive than weak acids of the same concentration

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How does concntration of hydrogen change as pH increases

It is a logarithmic scale, so the scale is 10^x when x is the pH change

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What is the difference between a strong acid and a concentrated acid

Acid strength tells you what proportion of the acids is ionises
Acid concentrationis how much acid there is in a volume of water

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What are metal oxides and metal hydroxides examples of

Bases

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What will happen if you react an acid and metal oxide and give an example with HCl and CuO

Acid + Metal Oxide –> Salt + Water
Hydrochloric acid + Copper Oxide –> Copper chloride + Water
2HCl + CuO –> CuCl2 + H2O

What will happen if you react an acid and metal oxide and give an example

Acid + Metal Oxide –> Salt + Water
Sulfuric acid + Potassium hydroxide –> Potassium sulfate + Water
H2SO4 + 2KOH –. K2SO4 + H2O

What does an acid and metal carbonate produce and give an example

Acid + Metal carbonate –> Salt + Water + Carbon dioxide
HCl + Na2CO3 –> 2NaCl + H2O + CO2

What is the reactivity series (elements)

Potassium
Sodium
Calcium
Magnisium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Hydrogen
Copper
Silver
Gold
Platinum

Metal + Acid —->

Salt + Hydrogen

What does a metal reacting with an acid tell you about reactivity

If it is a reactive metal, it will react vigotously and fast.
If it is a non reactive metal, it will react slowly with minimal efforvescence.

Metal + Water —>

Metal hydroxide + Hydrogen

What metals wont react with water

Non reactive ones like zinc iron copper and transition metals

Oxidation

Loss of electrons

Reduction

Gain of electrons

How can carbon be used in extraction of metals from ores.

Carbon is more reactive than the metal e.g. iron so it displaces it from the compound: Iron oxide + Carbon --> Iron + Carbon dioxide

How are metals higher than carbon in the reactivity series extracted

Electrolysis

What are redox reactions

When both reduction and oxidation occurs

What is a displacement reaction

When a more reactive metal will displace a less reactive metal from its compound

What is an ionic equation and how do you make one

Only particles that react and the proucts they form are shown. You get the equation Split it up into seperate elements with the charge on it See which ones dont change Get rid of them Done

What is electrolysis

When compounds are split using electricity. Positive ions move towards the negative cathode Negative ions move towards the positive anode

Can solid compounds be electrolysed and why. How do you fix

They can not because they are in fixed positions and can't move. You can either make them molten or dissolve them in water

What happens at each electrodes

Reduction happens at the cathode Oxidation happens at the anode

Explain the extraction of aluminium from its ore

Bauxite (aluminium ore) is mixed with cryolite so it has a lower melting point. It is melted in an electrolysis chamber Turns into a molten mixture of Al2O3 The aluminium oxide is electrolysed The Aluminium goes to the cathode where it is reduced The Oxygen goes to the anode where it is oxidised

What are the half equations for aluminium and oxygen when electrolysed and at which electrode and it is reduction or oxidation

Cathode- Al (3+) + 3e(-) --> Al: Reduction Anode- 2O(2-) --> O2 + 4e(-): Oxidation

What is the overall equation for electrolysis (splitting) of aluminium oxide

2(Al2O3) --> 4Al + 3O2

When a compound cant be melted, how would you perform electrolysis

Mix it with water and perform electrolysis with an aqeous solution

What are the rules for what is produced for electrolysis in an aqeous solution

Cathode- If less reactive than hydrogen, it will form: e.g. copper If more reactive than hydrogen, hydrogen will form Anode- If there is halide ions, the halide will form, if not then oxygen will form

What are the half equations for Hydrogen and water forming in electrolysis

Cathode: 2H(+) + 2e(-) --> H2 Anode: 4Oh(-) --> O2 + 2(H2O) + 4e(-)

Metal Hydroxide + Acide -->

Salt + Water

Acid + Metal carbonaate -->

Salt + Water + Carbon dioxide