Ionic Bonding, Alkali and Salts Flashcards
How can we classify substances as strong or weak acid and strong or weak alkalis?
pH Scale
What are the four 4 different types of indicators?
Litmus
Methyl Orange
Phenolphathlein
Universal Indicator
What Colour does Litmus turn when acid and alkaline?
Acid: Red
Alkali: Blue
What Colour does Methyl Orange turn when acid or alkali?
Acid: Red
Alkali:Yellow
What Colour does Phenolphthalein turn when acidic or alkaline?
Acidic: Colourless
Alkali: Pink
What is Neutralisation? What is the equation shown for this?
When acids and alkalis react forming a salt with a pH of 7
H+ (aq) + OH- (aq) —> H2O (l)
How does Neutralisation work?
Acid donates protons which are then accepted by the base.
Acid + Metal Oxide
Salt + Water
Acid + Metal Hydroxide
Salt + Water
Acid + Ammonnia
Ammonia Salt
Acid + Metal Carbonate
Salt + Water + Hydrogen
How to perform Titrations?
Using a pippette and pippette filter, add some alklali or acid (25 cm3) to a conical flask, along with two or three drops of indicator (phenophalein).
Fill a burette with the acid. Make sure you read below eye level to avoid parallax error and avoid spillage on your eyes
Using a burette, add the acid to the alkali a bit at a time to get more precise times at the end point. Also give conical flask a bit of a swirl to ensure it fuly mixes. Go slower to achieve accurate end point
The indicator changes colour when all the alkalis has been neutralised.
Record the volume of acid used to neutralise the alkali. It’s best to repeat this process a few times, making sure you get concordant results for improved reliabillity
How to work out the concentration using results from Titrations?
Work out how many moles from the substance you have
Write out the equation and find the molecular ratio to find the moles of the unkown substance
Work out concentration of unkown stuff
Why is it better to use indicators such as methyl orange, phenolpthalein etc: for titrations instead of universal indicators?
Universal Indicators are more gradual in colour change as it is more specific in pH. Therefore we cant find an accurate end point
Are all common salts of Na, K and Ammonium Soluble or insoluble?
Soluble
Are all nitrates soluble or insoluble?
Soluble
Are all common chlorides soluble or insoluble?
Soluble
except for eilver chloride and lead chloride
Are all common Sulfates soluble or insoluble?
Soluble
except for lead,barium and calcium sulfate
Are all common carbonates soluble or insoluble?
Insoluble
except for sopdium,potassium and ammonium ones
Are all common hydroxides soluble or insoluble?
Insoluble
except for sodium, potassium and calcium ones
How do you make insoluble salts?
Precipitiations Reactions
Mix two soluble salts to get your insoluble salt.
Add 1 spatula of soluble salt A into a test tube. Add water to dissolve it. You should use deionised water to make sure there arent any free ions about. Shake it thouroughly to ensure that all of Soluble salt A is dissolved. Then, in a seperate test tube do the the same with Soluble salt B.Tip the 2 soulutions into a small beaker, and give it a good stir to make sure it’s all mixed together. The new salt should precipitate out. Put out a folded piece of filter paper into a filter funnel and stick the funnel into a connical flask. Pou the contents of the beaker into the middle of the filter paper. Make sure that the soulution doesnt go above the filter- otherwise some of the solid could dribble down the side. Swill out the beaker with more deionised water, and tip this into the filter paper - to make sure you get all the precipitate from the beaker. Rinse contents of the filter paper with deionised water to make sure that all the salt has been washed away. Then just scrape the lead sulfate onto fresh filter paper and leave it fresh to dry in an oven
How to make Soluble Salts? If it isn’t sodium, potassium or ammonium
React an acid that contains one ion and you need insoluble base that has the other ion that you need (often a metal oxide or metal hydroxide)
Heat acid in water bath - this speeds up the reaction between acid and insoluble base. Do this in a fume cupboardto avoid releasing acid fumes into the room
Add base to acid - the base and acid will react to produce soluble salt. You will know when the base is in excess and all the acid had been neutralised because the excess solid will just sink to the bottom of the flask.
(It is better to have excess solid to make sure no acid is left)
Filter off the excess solid to get a solution containing salt and water
Heat the solution gentley, using a Bunsen Burner, to slowly evaporate off some of the water. Leave the solution to cool and allow the salt to crystallise. Filter off the solid salt and leave it to dry.
How can you make Soluble Salts when you have Sodium, Potassium and ammonium?
Use Titration method. Then carry out the raction using exactly the same volumes of alkali and acid but with no indicator to avoid contamination. The solution that remains only contains salt and water. Evaporate off some of the water and then leave the solution to crystalise. Filter off the solid and you will be left with a dry soluble salt.
Properties of Ionic Compounds?
.Have a giant ionic lattice structure
.Ions are held together in a closely packed 3D lattice arrangement by the attraction between oppositley charged ions.
.The electrostatic attraction between oppositley charged ions is very strong. Because a lot of energy is needed to overcome these strong electrostatic bonds, Therefore Ions have high melting and Boiling points
.Ionic Compounds are not electrical conductors when solid. But if you melt them, or dissolve them in water, they are able to conduct electrically.
What is an Acid?
A source of Hydrogen Ions, Ph is lower than 7
What is a Base?
A base is a substance that can neutralise an acid.
For a precipitation reaction. What will you observe as the reaction takes place?
Solid precipitate
For a precipitation reaction how will you know when you have added enough of the second reagent?
When there is no more solid precipitate
For a precipitation reaction, how can you remove any soluble impurities from the solid salt?
Wash with distilled water as the solid is not soluble
In a precipitation reaction, how can the salt be dried?
Dry in warm oven
When finding an insoluble salt, why is the excess solid added as a reagent
To ensure the reaction is complete
When finding an insoluble salt, how can you tell when the solid reagent is in excess?
How do you know when no more dissolves
When producing an insoluble solid, how is the excess solid removed?
Filtration
When producing an insoluble solid?
Increases rate of reaction which makes the reaction quicker
When producing a soluble salt, when should you stop heating the solution?
When it starts to crystallise
When producing a soluble salt, allow remaining solution to cool?
Low temp decreases the solubility
When producing a soluble salt, what could be done to recover the crystals without having to wait for all of the remaining water in the solution to evaporate
Filter the mixture
When producing a soluble salt, why should the crystals not be rinsed?
It is soluble so it can dissolve with the mixture
When producing a soluble salt, what would be a suitable means of wnsuring the crystals are dry?
Warm in an oven
