GCSE Chemistry- C4 chemical changes

What are the most reactive metals?

Potassium (K), sodium (Na), lithium (Li), calcium (Ca), magnesium (Mg), Aluminium (Al)

How can metals more reactive than carbon be extracted?

using electrolysis, as they cannot be displaced by carbon

What metals are in the middle of the reactivity series?

Carbon (C), Zinc (Zn), Iron (Fe), Tin (Sn), Lead (Pb) and Hydrogen (H)

What metals are extracted using reduction with carbon?

Zinc, Iron, Tin and lead

What are the least reactive metals?

Copper, Silver, Gold, platinum

What metals can be found naturally in its pure form?

Silver, Gold and Platinum

What happens when there is oxidation?

there is a loss of electrons (OIL)

What happens when there is reduction?

there is a gain of electrons (RIG)

What is redox?

reduction and oxidation happen together

Half equations: positive ions

eg. Mg2+ + 2e- -> Mg

Half equations: negative ions

Eg. 2Br- - 2e- -> Br2

Examples of common acids

Hydrochloric acid, Sulfuric acid, nitric acid

What is the chemical formula for Hydrochloric acid?

HCl

What is the chemical formula for sulfuric acid?

H₂SO₄

What is the chemical formula for nitric acid?

HNO₃

ionic equation

metal (s) + acid (aq) -> salt (aq) + hydrogen (g)

what happens when water is the solvent of the solution?

the product would be aqueous (aq)

How to name salts?

metal is from the metal and the non-metal is from the acid

What colour is an acid if there is universal indicator?

Red

What colour is neutral if there is universal indicator?

green

What colour is an alkali if there is universal indicator?

blue/purple

How are Acid+alkali equations neutral?

Acid (red/low pH) + Alkali (purple/high pH) -> Salt + water (green/netural)

Low pH + high ph -> neutral pH

What ion makes a substance acidic?

H+ ion (positive hydrogen ion)

What ion makes a substance alkali?

OH¯ ion (negative hydroxide ion)

why is water (H₂O) neutral?

there is a H+ ion and a OH¯ ion, therefore the charge is neutral

What does vinegar contain?

Ethanoic acid

What do all acids produce in solution?

produces H+ ions in solution as acids ionise to release the ions in the solution. In strong acids, every molecule is ionised to produce lots of H+ ions and is fully ionised.

What do strong acids (low pH) have more of compared to weaker acids (pH closer to 7)

Strong acids have much more H+ ions, whereas weak acids have less H+ ions

What do strong acids do in solution?

They fully ionise insolution

What happens in weak acids?

only some acid molecules ionise and produce some H+ ions- the acid is partially ionised

What is the chemical formula for carbonic acid?

H₂CO₃ ⇌ H+ + HCO3-

concentration vs strength of acid

imagine same concentration of vinegar and HCl (same number of molecules per unit volume). In the strong acid: HCl, all molecules of HCl ionises, whereas in the weak acid: vinegar, very few vinegar molecules ionises

What is concentration?

how diluted the acid is

What is strength of acid?

How easily the acid ionises

What is a base?

A group of compounds that are able to neutralise acids. They are split into two types: bases soluble in water- alkali, used in solution and bases insoluble in water- used as solid powders

What are bases that are soluble in water?

alkali, commonly used in solution

What are bases that are insoluble in water?

they are used as powders

What is neutrilisation?

A type of reaction occurring when an acid reacts with a base

What happens when an acid reacts with a base?

it becomes neutralised (pH7)

What happens when a base is neutralised by an acid?

it becomes neutralised (pH7)

Example of soluble bases (alkalis)

Sodium Hydroxide (NaOH), Lithium Hydroxide (LiOH), Potassium Hydroxide (KOH), calcium hydroxide (Ca(OH)2)

what makes an alkali an alkali?

Having OH- ions

Examples of insoluble bases

Calcium oxide (CaO), Magnesium oxide (MgO), Magnesium Carbonate (MgCO3), Sodium carbonate (Na2CO3)

What are typically signs of insoluble bases?

metal oxides and metal carbonates

Reaction between acids and soluble bases (alkali)

acid + metal hydroxide (alkali) -> salt (soluble ionic compound) + water (neutral)

acid + metal hydroxide -> salt + water

Reaction between acids and insoluble bases (metal oxides)

Acid + metal oxide -> salt + water

How will the reaction between acids and insoluble bases be neutral?

the insoluble base will dissolve in acid until there is no acid left (neutralisation)

Reaction between acids and insoluble bases (metal carbonates)

Acid + metal carbonate -> salt + water + carbon dioxide

What does carbon dioxide as a product mean in the reaction between acids and insoluble bases?

Gas is given off

Making salts RP method

1. add sulfuric acid to beaker

2. gently heat acid to speed up reaction

3. add a spatula of copper powder to beaker and stir with glass rod to distribute particles

4. keep adding more copper oxide until it no longer dissolves, ensure all acid has been heated

5. slowly filter solution to remove excess copper oxide

6. set up water bath and pour some solution into the evaporation basin

7. gently heat solution and stop when crystals begin to form

8. allow to slowly evaporate

what does a lower pH mean?

higher concentration of H+ ion

What scale is the pH scale

Logarithmic scale- goes up by powers of one

what is titration?

an experimental technique where a solution with a known concentration is used ti determine the concentration of a unknown solution.

titration RP method

1. fill burette with acid of unknown concentration

2. glass pipette is used to add 25cm3 of a known concentration to a conical flask

3. add indicator to alkali

4. slowly open the tap on the burette and wait until it changes colour to clear

5. measure the change in volume of burette to find concentration

concentration formula

concentration= moles (mol)/volume (dm3)

balanced symbol equation for titrations

H2SO4 2- + 2NaOH -> Na2SO4 + 2H2O

What is an ionic compound?

A negative ion (metal) and a positive ion (non-metal) in a compound

what is electrolysis?

to break down compounds using electricity, mostly to break down ionic compounds

What is a electrolyte?

an ionic compound that is melted or dissolved in water so that the ions are free to move

What happens to ions during electrolysis?

the ions discharge during electrolysis and turn to uncharged atoms

What are cations?

positive ions

what are anions?

negative ions

what are metals attracted to in electrolysis?

the cathode

what are non-metals attracted to in electrolysis?

the anode

What is the cathode?

The negative electrode

What is the anode?

The positive electrode

What are electrodes?

charged pieces of carbon used in electrolysis

What are uses of aluminium?

car bodies, cooking foil, airplanes, overhead cables

what are properties of aluminium

low density- lightweight, strong- durable, resistant to corrosion

Where is Aluminium found in?

Bauxite- contains Aluminium oxide (Al2O3)

Overall reaction of Aluminium oxide

2Al2O3 -> 4Al + 3O2

rules for electrolysis

if the non-metal is a halide ion (g7), then halogen discharged. If non-metal isn't a halide ion, oxygen (O2) is discharged

If the metal is more reactive than Hydrogen, hydrogen (H2) is discharged. If metal is less reactive than hydrogen, metal is discharged.

what is discharge?

The ion losing charge

nitrate ion

NO3 -

Sulfate ion

SO4 2-

Carbonate ion

CO3 2-

Hydroxide ion

OH -

Hydrogen ion

H +

Ammonium

NH4 +

Phosphate ion

PO4 3-