Acid Base Salt Preparation + Chemical Tests Flashcards
Give four examples of the type of compounds that are alkalis
Metal hydroxides, some metal oxides in water, some metal carbonates in water, ammonia in water
Which metal oxides are soluble in water
Potassium, sodium, calcium
Give an example of a metal carbonate that is soluble in water
Sodium carbonate
Copper oxide and sulfuric acid react to give what?
(State the colour change aswell)
Copper sulfate + Water
Black copper oxide becomes blue solution
Metal oxide + acid—-)
Salt + water
Metal hydroxide + acid—-)
Salt + water
Carbonate + acid—-)
Salt + water + carbon dioxide
Explain why water is produced when a metal oxide reacts an acid
Because the O2- ions in the oxide react with the H+ ions in the acid to produce H2O
Explain why water is produced when a metal hydroxide reacts with an acid
Because the OH- ions in the hydroxide react with the H+ ions in the acid to produce H2O
State the product when copper carbonate reacts with sulfuric acid
And state the colours of the reactants and products
Copper sulfate + carbon dioxide + water
Copper carbonate is green, copper sulfate will be blue
(Remeber that when a metal carbonate reacts with an acid it’s a neutralization reaction,
And whenever copper carbonate reacts with any dilute acid a blue salt is formed)
When magnesium reacts with hydrochloric acid,
State the products
And the colour of the product
And state why the color is why it is
Magnesium chloride + hydrogen
Colourless
Because the magnesium dissolves
State what is the difference when aluminum reacts with cold dilute acid and when it reacts with warm dilute acid
When reacting with cold acid, a thin layer of aluminum oxide is formed
When reacting with warm acid, the thin layer is removed and it reacts more vigorously
What is a base
A substance that can neutralize an acid
What is an alkali
A source of OH- ions in a solution
What is the product when ammonia reacts with an acid
An ammonium salt
All sulfates are soluble except
Lead, barium, calcium
Nitrates
(Solubility:)
All nitrates are soluble
Is copper chloride soluble
Yes
(Because all chlorides are soluble except silver and lead)
Is magnesium nitrate soluble
Yes
(Because all nitrates are soluble)
Is lead chloride soluble
No
(Because all chlorides are soluble except silver and lead chloride)
Is lead sulphate soluble
No
(All sulfates are soluble except from lead, barium and calcium)
Carbonates
(Solubility:)
Only potassium sodium and ammonium carbonates are soluble,
The rest are insoluble
Hydroxides
(Solubility:)
Only potassium, sodium and calcium are soluble
(The rest are insoluble)
Is calcium sulfate soluble
No
(Because all sulfates are soluble except lead, barium and calcium)
Is lithium sulfate soluble
Yes
(Because all sulfates are soluble except lead, barium, calcium)
Is magnesium carbonate soluble
No
(Only potassium , sodium and ammonium carbonates are soluble. All other carbonates are insoluble)
Is ammonium carbonate soluble
Yes
(Only sodium, potassium and ammonium carbonates are soluble. The rest are insoluble)
Is magnesium hydroxide soluble
No
(Only potassium, sodium and calcium hydroxide de are soluble. The rest are insoluble)
Is ammonium hydroxide soluble
Yes
(Even though only sodium, potassium and calcium hydroxide are soluble, all compounds of ammonia will always be soluble)
Sulfates
(Solubility:)
All sulfates are soluble, except lead, barium, calcium
Explain why a different method be required to make soluble salts using potassium, sodium or ammonium, compared to other methods
Because sodium potassium and ammonium are soluble in water
So once the reaction has been complete with the acid, the excess solid would just dissolve
So you wouldn’t know when the reaction is complete and how much volume exactly of solid was required to neutralize the reaction
What is the general formula to make a soluble salt
Acid + insoluble base —) soluble salt + water
Why method could you use to make a soluble salt with potassium, sodium or ammonium in it
Use a titration
When making hydrated copper sulfate crystals, why could you not simply evaporate them to dryness
Bc then you would be left with anhydrous salt, a white powder
What colour is anhydrous copper sulfate
White powder
What is water of crystallization
When water is chemically bonded to the salt, so forms part of its crystal structure
What is a risk when evaporating crystals simply with a Bunsen burner
The high temperatures could cause a thermal decomposition reaction to occur, so the crystals may begin to break down
What is the purpose of adding an excess amount of insoluble base, when making a soluble salt
So that you know when the neutralization reaction has been completed, so when all the acid has been neutralized
Give the word equation to make copper sulfate crystals
Copper oxide + sulfuric acid —) hydrated copper sulfate crystals
Give the word equation to create hydrated magnesium sulfate crystals
Magnesium + sulfuric acid —-) hydrated magnesium sulfate
Give two examples of substances that when creating soluble salts with them, it is not required to heat the solution
Carbonates and magnesium
(Because they react the same with cold acids as they do with warm acids)
Explain how to make hydrated copper sulfate crystals (a soluble salt) (8)
1)measure out sulfuric acid into a beaker and heat under a Bunsen burner so that the reaction will be faster
2) add the insoluble base in excess, and keep adding until a saturated solution is formed
3)filter out the excess insoluble base with filter paper, so you are left with a solution of the salt and water
4)pour solution into an evaporating basin and heat in a water bath to evaporate the water and to make the solution concentrated
5) stop heating when solution is saturated and leave to crystallize. Test the presence of crystals with a glass rod
6) filter out the excess solution and collect the crystals on the filter paper
7) dry with a blotting towel
Explain how to make a soluble salt with a titration (9)
1) add 25cm3 of acid with a pipette to a conical flask
2)add phenolphthalein indicator and place under a white tile to see the colour change
3)add the alkali to a burette and keep adding until the solution changes colour
4)measure the end volume
5) add exactly the same amount of acid and alkali to a new clean flask
6)heat in a water bath to evaporate the water, until solution is concentrated
7) allow to crystallize and test with a glass rod
8) filter off the excess solution with filter paper
9) dry with a blotting towel
Explain how to make an insoluble salt
1) add the first insoluble salt to a beaker, then add the second insoluble salt
2)filter off the precipitate with filter paper
3) rinse with distilled water to remove contaminations
4) dry in a warm oven
Give the general formula to make an insoluble salt
Soluble salt + soluble salt —) insoluble salt + soluble salt solution
Predict what two solutions silver chloride is made of
Silver nitrate and potassium chloride
(Bc remember when making insoluble salts, the first solution is usually a compound in nitrate form and the second is usually potassium, sodium or ammonium)
Predict two substances that barium sulfate is made of
Barium nitrate and potassium sulfate
To make an insoluble salt reaction is also called..
À prédication reaction
What colour is the precipitate when making silver chloride
White precipitate
Explain how to carry out a flame test
1)dip a loop of unreactive wire such as Nichrome or platinum in hydrochloric acid
2)hold under a blue flame of a Bunsen burner until there is no color change, which means that the lop has been cleaned and is free of contamination
3)dip the rod into the solid sample, and hold on the edge of a Bunsen burner in a blue flame, and observe colourless change
In the flame test, give examples of two metals that you can use for the loop of wire
Nichrome or platinum
Flame test colour of lithium ions:
Red
Flame test colour of sodium ions:
Yellow
Flame test colour of potassium ions:
Lilac
Flame test colour of calcium ions:
Orange-Red
Flame test colour of copper ions:
Green-Blue
During the flame test, why is it important to have the loop of wire free from contamination
1)because the flame test will only work if there is one type of ion present
2)mixing two or more ions could give inaccurate colours
Why is it important to not let the wire get too hot in a flame test
Otherwise the heat would turn the wire red, and then this could be confused with other colours
Explain how you can carry out the test where sodium hydroxide reacts with cations
1)dissolve the salt into distilled water, and put 1cm3 into a test tube
2)add sodium hydroxide solution
3)observe the precipitate formed
Explain why sodium hydroxide can be used to test the presence of metal cations, in a precipitate reaction
Because sodium hydroxide is the only soluble hydroxide, which will thus react with a metal salt.
This will produce a metal hydroxide which is usually insoluble, thus forming a precipitate
Which ions turn blue in a precipitation test reaction
Copper 2+ ions
Which ions turn green in a precipitation test reaction
Iron (ii) ions
Which ions turn orange-brown in a precipitation test reaction
Iron (iii) ions
For which ions, could you not use a solid form of when performing a precipitation reaction on them,
And explain why
Copper(ii)
Iron (ii)
Iron(iii)
Because you wouldn’t be able to see whether a precipate has formed, because a solid is already present
What happens to the colour of iron (ii) hydroxide when it is left for a while,
and explain why,
And state the product that is formed then
The top turns orange- brown
because the iron(ii) hydroxide reacts with the oxygen in the air
To form iron (iii) hydroxide
What colour is the predicate when iron (ii) reacts with sodium hydroxide
Green precipitate
Give the ionic equation when iron (iii) reacts with sodium hydroxide in a precipitation reaction
Fe3+(aq) + 3OH-(aq) —-) Fe(OH)3 (s)
(Remember that you can leave out the sodium ions because they are spectator ions)
(And the Fe3+ ions are in liquid form, bc otherwise if they were in solid you wouldn’t know when the reaction was over)
State two different tests for ammonium ions, in cold and with heat
In cold:
Add sodium hydroxide to ammonium ions, and ammonia gas will be formed which you can smell
With heat:
Ads sodium hydroxide to ammonium ions, and ammonia gas will be given off, which can be tested with glue litmus which will turn red in the presence of ammonia gas
What is the chemical formula for the precipitate formed for the test for copper (ii) ions
Cu(OH)2
(Because remember that copper (ii) in solution reacts with sodium hydroxide to form copper hydroxide)
Give the balanced symbol equation of when solid ammonium chloride reacts with sodium hydroxide
(Remember that this is a precipitation reaction to test for the presence of ammonium ions)
NH4Cl(s) + NaOH(aq) —-) NH3(g) + NaCl(aq) + H2O(l)
Give the word equation of when solid ammonium chloride reacts with sodium hydroxide in a precipitation reaction
Solid ammonium chloride + sodium hydroxide —-) Ammonia gas + sodium chloride + water
Give the ionic equation of when ammonium ions react with sodium hydroxide in a precipitation reaction
NH4+(aq) + OH-(aq) —-) NH3+(g) + H2O(l)
Explain the test for carbonates
Add dilute hydrochloric acid to solution of carbonate
If fixing is present, this means that a gas has been given off
So bubble the gas through limewater,and if it turns milky, then carbon dioxide is present, so you solution had a carbonate
Which one acid could you not use when testing for the presence of carbonates and explain why
Can not use sulfuric acid because it creates an insoluble salt,
which will create a layer on top of the test tube
And stop carbon dip de gas from coming out
Explain the test for sulfates
Add dilute hydrochloric acid to a barium chloride solution
Add this solution now to a solution of the salt you are testing for which has been in distilled water
A white precipitate of barium sulphate should form, meaning sulfates are present
What are the two types of anions in which there are two different acids that could be used in the test, and which is the type of anion in which only one type of acid can be used
To test for carbonates and sulfates, you can either use hydrochloric acid or nitric acid.
But to test for halides, you can only use nitric acid
Why can you not use sulfuric acid in the test for sulfates
Because then the barium sulfate will be formed anyway, so not an accurate test to test for sulfates
Explain the test for halides
1)add nitric acid to a solution of silver nitrate
2)add this to a solution of the suspected halide
3)if white, then chlorides are present
If cream, then bromides are present
If yellow, then iodides are present
When doing a test to test for halides, the colour of the precipitate is yellow. State the name of the precipitate
Silver iodide
When doing a test to test for halides, the colour of the precipitate is cream. State the name of the precipitate
Silver Bromide
When doing a test to test for halides, the colour of the precipitate is white. State the name of the precipitate
Silver chloride
Name the two solution you need to do a test for halides
Nitric acid and silver nitrate solution
Name two solutions you could use to do a test for sulfates
Hydrochloric acid and barium chloride
What is the purpose of adding an acid to the tests for sulfates
Because the acid removes any traces of other anions, by reacting with them
Because otherwise the other anions could also react with the barium to form a white precipitate,
Describe the test for hydrogen
Place a lighted splint above the test tube
If there is a squeaky pop then hydrogen gas is present
For which gas test does the squeaky pop occur,
And why does this noise occur
For hydrogen gas
Because the hydrogen from the test tube reacts with the oxygen in the air to form water
Describe the test for oxygen gas
Light a splint and then blow it out to create a glowing splint
Place in the test tube, and the glowing splint should be reignited if oxygen gas is present
Describe the test for carbon dioxide
Place a bung and test tube over solution you are testing the gas for.
Bubble through limewater, if limewater turns milky (if a white precipate is formed), then carbon dioxide is present
Give the chemical name of limewater
And give the name of the product formed when limewater reacts with carbon dioxide
Limewater= calcium hydroxide
Product= Calcium carbonate (the white precipitate that makes the reaction milky)
Explain what will happen if carbon dioxide continues to bubble through limewater for an extended amount of time
The carbon dioxide will eventually react with the calcium carbonate that was produced
To form calcium hydrogen carbonate
Which is soluble so will dissolve in the solution,
Giving you a colourless solution
What color will the test tube be if carbon dioxide bubbles through the limewater for a long time and why
Colourless
(Because it reacts with the calcium carbonate to form calcium hydrogen carbonate, which is soluble so dissolves in the solution)
Give the balanced symbol equation of when carbon dioxide bubbles through lime water for a long time
CO2(g) + CaCO3(s) + H2O(l) —-) Ca(HCO3)2 (aq)
Give the test for chlorine gas
Place damp blue litmus paper in the test tube
First If chlorine gas is present, it will turn damp blue litmus paper red frost as the chlorine will dissolve in the water to form an acidic solution
Then it will bleach the paper turning it white
Give the test for ammonia gas
Place damp red litmus paper in the test tube
Should turn the red litmus paper blue
Because ammonia gas is alkaline
Give the test for if water is present
Add anhydrous (ii) copper sulfate to the solution
Add a few drops of water,
Should turn the white anhydrous copper(ii) sulfate blue if water is present
A student mixes a solution of silver nitrate and sodium chloride together to make silver chloride and sodium nitrate
State what colour the precipitate is
White precipitate
(Remember this is a classic example of making an insoluble salt)
Give the full word equations of two common reactions used to make insoluble salts
-barium nitrate + potassium sulfate. —-) barium sulfate + potassium nitrate (white precipitate of barium sulfate)
-silver nitrate + sodium chloride —-) silver chloride + sodium nitrate (white precipate of silver chloride)
Explain how to obtain a pure dry sample of a salt solution
1)heat in an evaporating basin, to evaporate some of the water
2)keep heating until crystals form until, for a saturated solution, test with a glass rod
3)leave to cool, so that further crystals form (solubility decreases in cool temperatures )
4)remove the crystals with filtration
5)heat in a warm oven, to evaporate the rest of the water
6)pat dry with a blotting towel
