C4

Acids and bases

  • If it’s Ph is higher than 7 its an alkaline

  • If it’s pH is lower than 7 its Acidic

  • If the pH is 7 Its pure WATER


  • You can use an indicator to tell pH, based on its colour

  • or a pH probe which measures pH electronically

  • Acids Are proton doners, donating H+ ions which are just protons

  • Alkaline are proton acceptors with OH- ions:

  • H+ + OH- = H2O

Strong acids

Think about it like this- It’s an acids job to donate protons/ H+ ions The better it is at its job, the stronger it is as an acid, So strong acids that completely disassociate with their H+ ions Giving them up completely in water are much stronger than acids that still keep the H+ ions in a partial disassociation. Like how a waiter serving food is good if they serve the food and then disassociate with the food instead of only partially disassociating with the plate holding onto it with a death grip a you try to eat the food off it only for them to reverse the serve and take the plate back again.

  • Acids form H+ ions when dissolved in water

  • Strong acids Completely disassociate to and release H+ ions in water in an irreversible reaction

  • They fully ionise meaning that they split up in to their individual ions (The ions are atoms with full outer shells)

  • E.g.: HCl, Sulfuric acid, Nitric acid

  • These have a lower pH


  • Weak acids only partially disassociate into their ions, in a reversable reaction

  • Only some of the original acid molecules disassociate into ion

  • e.g.: Ethanoic acid, Citric acid

  • These have a higher pH

The more H+ ions, the faster the rate of reaction, So strong acid are more reactive than weak acids at the same concentration.


pH is dependant on Both concentration and Strength:

  • The higher the Strength the more H+ ions there will be as Strong acids, fully disassociate, creating a higher concentration of acids

Titrations

This is an experiment that lets you find out exactly how much acid is needed to neutralise a quantity of alkali or vice versa:

  1. Use a pipette and pipette filter to add a set volume of alkali to a conical flask

  2. Add 2 or 3 drops of indicator to the alkali solution (Phenolphthalein)

  3. Use a funnel to fill a burette with some acid of a known concentration

  4. Record the initial volume of the burette

  5. Use the burette to slowly add the acid to the alkali stirring as you go

  6. Once the colour change is reached shut the tap to the burette and record the final volume

Things that could go wrong

  • is a parallax error when reading the measurements, -Record with eye level in line with the measurement

  • Anomalous results - Repeat the experiment multiple times


Picking an indicator

  • You need an indicator with a sudden colour change like:

  • Phenolphthalein OR Methyl

  • This is to ensure that it is easy to tell weather the solution is either acid or alkali

Reactions of acids

  • All metal oxides react with acids to form a salt and water

  • And all metal Hydroxides react with acids to form a salt and water.

  • And all metal carbonates react with acids to form a salt, water and carbon dioxide

  • And metals react with acids to form a salt, and hydrogen

  • And metals can react with water to form a Metal hydroxide + hydrogen

  • For example:

Thx CGP

How to balance these equations?

  • Firstly you need to know the actual symbols of each substance

  • Then you need to split them up into their ions (including their charges after gaining full outer shells)

  • Then you react the elements that were not in a compound before and have opposite charges

  • Making sure that water is one of the products

  • Then after writing down the new compounds formed you balance the equation

  • Now do a worksheet.

The reactivity series

This follows the reactivity of metals in order with the only ones you have to worry about going from most the least reactive are:

Now If you forget this just know that it is determined my the shielding and how hard it is for the metals to lose or gain electrons so far down group 1 metals, would be more reactive then far up group 2.


  • The faster hydrogen is released in a reaction the more reactive the metal

  • The higher the temperature change in a reaction the more reactive the metal

Separating metals from metal oxide

  • Oxidation → The gain of oxygen / The loss of electrons / The loss of hydrogen

    • Reduction → The loss of oxygen / The gain of election/ The gain of hydrogen (WELCOME BACK!!)

  • Oxidation and reduction happen simultaneously with different elements within a reaction (Redox reaction)

  • Oxides are commonly ores of the metal

  • Carbon is commonly used to reduce certain metal ores (Carbon gets oxidized to CO2 in the reaction)

  • However it can only oxidize metal ores that are less reactive then it:

  • Zn, Fe, Cu

  • The rest are reduced by electrolysis

  • Some elements are so reactive that it cran’t react naturally to from an ore


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  • ‘cus

  • Many

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Redox reactions

  • Oil Rig CHOO CHOO!!!

  • Oxidation is loss reduction is gain

  • Redox equations can be split into 2 half equations

  • Each half equation is either oxidation or reduction

  • It cran’t be both its either or

  • A displacement reaction is when a more reactive element displaces a less reactive element from its compound

  • Displacement reaction are redox reactions

Turning things into ionic equations:

  • Write out the entire reaction in symbol form

  • Identify the charge of the metal in the ionic compound

  • remove the nonmetal

  • write out the equation with the charges of the metals

Electrolysis

  • Electrode - Electrically charged rod

  • Electrolysis - Using electricity to break down electrolytes to form elements

  • Electrolyte- A dissolved or molten ionic compound


  • Electrolysis is using electricity to separate Molten or dissolved ionic compound back into their original elements

  • This is done by first getting them molten/ dissolved

  • as the ions and particles can’t move freely in solid form

  • But they can move freely when dissolved in certain solutions or molten

  • Meaning that they can conduct electricity

  • This means that they can be used to complete a circuit

  • So electrodes are attached to oppositely charged ends of a circuit and dunked into the electrolyte, Attracting differently charged ions, thus separating them


These two ends have different names- one is the-

Cathode

  • Cathodes are negatively charged electrodes

  • So they have a current of electrons flowing through them

  • So when Positive ions move towards them due to forces of electrostatic attraction

  • So these positive ions get Reduced as that gain full outer-shells

  • And are no longer dependant on oxygen for that

  • Usually metals


Anode

  • These are positively charged electrodes

  • So they Have a lack of electrons

  • So negative ions move towards them due to forces of electrostatic attraction

  • The ne negative ions lose electrons, Becoming oxidised

  • Usually nonmetals


This creates a flow of electrons as electrons get transferred throughout the circuit

Forming uncharged elements as the surplus electrons a discharged from the electrolyte via the electrodes


This process can be used to Extract pure metals from their ores:

This works because metals positive ions meaning that they will be attracted to the cathode in electrolysis, whilst the non-metals into ore will be attracted to the anode

This is used on metals that are too reactive to be reduced by carbon e.g. aluminium:

  • Positive Aluminium ions are attracted to the

The circuit is completed by the non-metal giving up electron at the positively charged electrode, which travels up the circuit as they are attracted to the positive side, then bushed out the other end to give the metals electrons to make them become neutral at the other end

Electrolysis of Aqueous solutions

This means that Hydrogen ions from the water will be added to the mix meaning that:

At the cathode:

  • For metals more reactive than Hydrogen, hydrogen gas will be produced

  • For metals less reactive than hydrogen a solid layer of the metal is made instead

At the anode:

  • If halogen ions (Group 7 ions) are there then their molecules will be formed

  • If not then OH- ions will be turned into oxygen


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