Topic 4 Flashcards
What does acid + metal carbonate make?
acid + metal carbonate -> salt + water + carbon dioxide
What does acid + metal hydrogen carbonate make?
acid + metal hydrogen carbonate -> salt + water + carbon dioxide
What does acid + metal hydroxide make?
acid + metal hydroxide -> salt + water
What does acid + metal oxide make?
Acid + metal oxide -> salt + water
What does acid + metal make?
acid + metal -> salt + hydrogen
What does soluble acid and soluble base make?
soluble acid + soluble base -> soluble salt + water
What is the ion of hydrogen carbonate?
(HCO3)-
What is an alkali?
Soluble base
What is the procedure to get a salt from soluble acid and soluble base reaction?
Procedure: Neutralisation by titration. It uses a known concentration of a soluble acid, which is neutralised by an alkali. It forms a salt solution that is dissolved in water.
Purification: Evaporation. Since a salt solution is produced the salt needs to be isolated. This is done by evaporation to remove most of the water. The crystalline salt can be dried on paper or left in a warm oven
What does a soluble acid and insoluble base make?
Soluble acid + insoluble base -> soluble salt + water + (carbon dioxide)
What is the procedure to get a salt from soluble acid and insoluble base reaction?
Procedure: Neutralisation. Add excess insoluble base/carbonate so that all acid fully reacts. Forms a salt solution (dissolved in water). Can do titration aswell.
Purification: Filtration and evaporation. Filtering the final solution removes any unreacted solid bases and evaporation is done to isolate the salt.
What is water of crystallisation?
A crystalline salt that is hydrated or chemically combined with water
What is an anhydrous salt?
A salt that is heated to complete dryness. A compound with all water molecules removed
How to find the amount of water associated with a salt experimentally?
- An accurate mass of hydrated salt is heated in a crucible to drive off all the water present
- The mass of the heated salt is recorded
- The salt is heated again until constant mass is obtained. This is now the anhydrous salt
Calculation: mass of hydrated salt - mass of anhydrous salt = mass of water
What does a soluble salt + soluble salt make?
Soluble salt + soluble salt -> insoluble salt + soluble salt
What is the procedure to get a salt from a reaction between two soluble salts?
Procedure: Precipitation. When two ionic salts are combined, they can form an insoluble salt; a precipitate.
Purification: Filtration. Filtering a mixture separates the insoluble salt as the precipitate
Purification: Washing and drying. Washing the precipitate to remove soluble impurities. Oven drying to obtain dry salt
If there is a reaction between two soluble salts AB and CD, what will the products be and which will be soluble and insoluble?
AB + CD -> AD (soluble) + BC (insoluble)
4 common acids
Hydrochloric acid (HCl)
Sulfuric acid (H2SO4)
Nitric acid (HNO3)
Ethanoic acid (CH3COOH)
4 common bases
Sodium hydroxide (NaOH)
Potassium hydroxide (KOH)
Sodium carbonate (Na2CO3)
Calcium carbonate (CaCO3)
What compounds are soluble?
Group 1 and NH4+(ammonium)
Are nitrates soluble?
All nitrates are soluble
Are carbonates soluble?
All carbonates are insoluble except those of group 1 and (NH4)2CO3
Are chlorides soluble?
All chlorides are soluble except AgCl and PbCl2
Are sulphates soluble?
All sulphates are soluble except CaSO4, PbSO4 and BaSO4
Are hydroxides soluble?
All hydroxides are insoluble except for those of group 1 and group 2 are slightly soluble
Characteristics of acids
- strong acids are corrosive
- weak acids taste sour
- acids turn litmus paper red
- pH below 7
- acids contain hydrogen (however not all things with hydrogen are acidic)
- acids react with alkaline
Characteristics of bases
- can be used as soaps and cleaning solutions
- turn litmus paper blue, turns universal indicator dark green, blue and purple
- react with acids
- pH above 7
- corrosive
What is a hydrogen ion?
A proton
What is an acid?
A proton donor
What happens to an acid when added to water?
Disassociates (split up) into H+ ions and negative ions (anions)
Why must an acid have hydrogen?
To donate a proton
What is a base?
A proton accepter
What do bases do when added to water?
Disassociate (split up) into OH- ions and positive metal ions (cations)
What is the net ionic equation for all acid and base neutralisation?
OH- + H+ -> H2O
What happens to a strong acid in water?
Fully disassociates in water to H+ ions. All H+ ions are donated and separate from the anions
What happens to a weak acid in water?
Partially disassociates in water into H+ ions. Some H+ ions are donated and the system forms an equilibrium
When do ammonium salts decompose?
When mixed with a strong base
Equation for ammonium salt
ammonium salt -> salt + water + ammonia gas (NH3)
Describe the stages in the preperation of a sample of dry copper sulfate crystals using sulfuric acid and copper oxide. Include a balanced equation. (7)
- React excess copper oxide with sulfuric acid
- Stir and heat mixture in a conical flask
- Filter excess black solid (copper oxide)
- Concentrate solution by heating in an evaporating basin
- Leave to stand and cool slowly to form crystals
- Dry crystals between filter papers/in oven
H2SO4 (aq) + CuO(s) -> CuSO4(aq) + H2O(l)
What are most non-metal oxides?
Acidic
What are most metal oxides?
Basic
What is amphoteric?
Some species are able to react like an acid and a base. Aluminium hydroxide is an example when it reacts with HCl it is a base and when it reacts with NaOH it is an acid.
What is amphiprotic?
Some species are able to donate and accept protons. Water is an example as it can accept a proton to be H3O+ or lose an electron to be OH-
What’s the easiest way to test oxide?
To observe a reaction
What do acidic and amphoteric oxides react with metal carbonates to form?
carbon dioxide gas
What do acidic oxides do?
Dissolve in water and lower the pH (test with universal indicator)
What do basic and amphoteric oxides do?
React with acids and be neutralised
What is limewater?
Name for a saturated aqueous solution of calcium hydroxide Ca(OH)2
What is limestone?
A sedimentary rock comprised mainly of calcium carbonate CaCO3
What is limewater used for? What does a positive result look like?
Test for carbon dioxide. Solution turns cloudy if carbon dioxide is present
Why does a positive result for carbon dioxide turn solution cloudy?
The carbon dioxide and limewater react to produce water in addition to calcium carbonate (chalk). When it’s produced it precipitates and solid particles of chalk appear, this makes the liquid appear milky.
What is quick lime?
Calcium oxide (CaO)
How do you turn limestone into quick lime?
Heat up (CO2 is lost) making CaCO3 into CaO
What is slaked lime?
Calcium hydroxide as a solid Ca(OH)2
How do you turn quick lime into slaked lime?
Hydration, adding water. Heat is lost.
How do you turn slaked lime into limewater?
Add more water
How do you turn limewater back into limestone?
Recarbonation. Add back CO2. Water is lost
Write the symbol equation for CaO is formed by decomposition of CaCO3?
CaCO3(s) -> CaO(s) + CO2(g)
Write the symbol equation for Ca(OH)2 is formed by addition of water to CaO?
CaO(s) + H2O(l) -> Ca(OH)2 (s)
Write the symbol equation for CaCO3 is formed by bubbling CO2 through a solution of Ca(OH)2 in the form of limewater?
Ca(OH)2 (aq) + CO2 (g) -> CaCO3 (s) + H2O (l)
What is formed when excess carbon dioxide is bubbled though limewater?
Calcium hydrocarbonate
Common uses of limestone?
- Building materials
- Manufacture of cement
Common uses of CaO?
- Wastewater treatment
- Neutralisation of acidic soil
How do you test for ammonia gas?
Add damp red litmus paper.
Observations: Turns it blue (ammonia is a base), splint test is uneffective
How do you test for chlorine gas?
Add damp blue litmus paper
Observations: Turns red (HCL produced), turns bleached (HOCl produced), puts out lit splint
How do you test for hydrogen gas?
Lit splint test
Observations: squeaky popping sound (hydrogen is flammable)
How do you test for oxygen gas?
Glowing splint test
Observations: Reignites splint
How do you test for carbon dioxide?
Bubble gas through limewater
Observations: White precipitate forms, turns cloudy
How do you test for sulfur dioxide?
Add potassium permanganate paper (purple)
Observations: Turns purple colourless (MnO4 is reduced), puts out lit splint
How do you carry out a flame test?
- Dip a clean wire loop into a sample of the compound being tested
- Put the loop into the edge of the roaring blue flame from a bunsen burner
- Observe and record the flame colour
What colour does barium ion (Ba2+) turn in the flame test?
Light green
What colour does calcium ion (Ca2+) turn in the flame test?
Orange-red
What colour does copper ion (Cu2+) turn in the flame test?
Blue-green
What colour does lithium ion (Li+) turn in the flame test?
Red
What colour does potassium ion (K+) turn in the flame test?
Lilac
What colour does sodium ion (Na+) turn in the flame test?
Yellow
Why is sodium hydroxide and ammonium hydroxide used to test for cations?
Because they form insoluble hydroxides which result in a precipitate
What are the products when metal reacts with water?
Metal hydroxide and hydrogen gas
List the abundance of elements from most to least
Oxygen (46.6%)
Silicon (27.7%)
Aluminium (8.1%)
Calcium (6.6%)
Iron (5.0%)
Which metals can be found as elements?
Some unreactive metals like gold and silver. They are called native metals
How are most metals found naturally?
In rocks called ores. They are in compounds, chemically bonded to other elements ex oxygen as metal oxides
How do you isolate a pure metal from the ore?
The metal compound must undergo reduction to free the metal. Reduction is the loss of oxygen from the metal oxide. The method of extraction depends on the position of the metal in reactivity
How are metals above carbon extracted?
Electrolysis
How are metals below carbon extracted?
Reduction using carbon, coke or charcoal
What is the most common aluminium ore?
Bauxite (Aluminium oxide Al2O3)
Why is bauxite mixed with cryolite?
To help it melt easier because bauxite has a very high melting point (200°C)
What is the half equation that happens in the extraction of aluminium from aluminium oxide at the anode and cathode?
Anode: 2(O)2- -> O2 + 4e- and O2 + C -> CO2
Cathode: Al3+ + 3e- -> Al
What is the reactivity series of metals?
Potassium
Sodium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Hydrogen
Copper
Silver
Gold
What happens in a displacement reaction?
The metal in a compound is replaced by the more reactive metal to form a new compound
How do you test for hydroxide?
Universal indicator turns red litmus paper blue
What is electropositivity?
the tendency of an atom to donate electrons and form positively charged cations.
What is electronegativity?
the tendency of an atom to attract electrons when forming a chemical bond
Why is an element further in a group more reactive than another?
The further away from the nucleus the valence electrons are, it is easier to lose them to become a cation
Why is an element further in a period more reactive than another?
The more protons in the nucleus, the harder it is to lose a valence electron
If you add 2 drops of dilute NaOH solution and there is no precipitate. Then you add NaOH solution and heat test gas with red litmus and it turns blue what is the cation?
Ammonium (NH4)+
If you add two drops of dilute NaOH solution and there is a white precipitate. Then you add excess NaOH solution and the precipitate remains what is the cation?
Calcium (Ca)2+
If you add two drops of dilute NaOH solution and there is a white precipitate. Then you add excess NaOH solution and the precipitate disappears. Then add two drops and then excess NH3 solution and the white precipitate forms. What is the cation?
Aluminium (Al)3+
If you add two drops of dilute NaOH solution and there is a white precipitate. Then you add excess NaOH solution and the precipitate disappears. Then add two drops and then excess NH3 solution and the white precipitate forms and disappears. What is the cation?
Zinc (Zn)2+
If you add two drops of dilute NaOH solution and there is a green precipitate. What is the cation?
Iron (II)
(Fe)2+
If you add two drops of dilute NaOH solution and there is a brown precipitate. What is the cation?
Iron (III)
(Fe)3+
If you add two drops of dilute NaOH solution and there is a blue precipitate. Then you add two drops and excess NH3 solution and blue precipitate stays and becomes a deep blue solution. What is the cation?
Copper (II)
(Cu)2+
If you add Ba(NO3)2 solution and a white precipitate forms. What is the anion?
Sulphate (SO4)2-
If you add Ba(NO3)2 solution and there’s no precipitate. Then add dilute HCl solution to a new sample and bubbles of gas form. Then if it turns limewater cloudy. What is the anion?
Carbonate (CO3)2-
If you add AgNO3 solution and a white precipitate forms. Then add dilute NH3 solution and the precipitate disappears. What is the anion?
Chloride (Cl)-
If you add AgNO3 solution and a yellow precipitate forms. What is the anion?
Iodide (I)-
If you add AgNO3 solution and a cream precipitate forms. What is the anion?
Bromide (Br)-
If you add lead nitrate solution and a yellow precipitate forms. What is the anion?
Iodide (I)-
If you add aluminium foil or devarda’s alloy and ammonia gas evolved red litmus paper to blue. What is the anion?
Nitrate (NO3)-
What’s the difference between a strong acid and a weak acid? (2)
Strong acids completely or fully ionises / completely or fully dissociates / completely or fully splits into ions; [1 mark]
Weak acids partially or incompletely ionises or dissociates or splits into ions /does not ionise fully; [1 mark]
What does acid + ammonia make?
ammonium salt
What does base + ammonium salt make?
Salt + ammonia + water
Why does the carbon anode in the electrolysis of carbon need to be replaced regularly?
The anode needs to be replaced regularly because it is degraded over time due to the reaction of the carbon in the graphite with oxygen gas into carbon dioxide.
State two functions of coke in the blast furnace
To burn / provide heat;
To make carbon monoxide;
What does the coke do when it first enters the blast furnace?
reacts with oxygen in the hot air to form carbon dioxide
C(s)+O2(g)->CO2(g)
What does the carbon dioxide do in the blast furnace?
React with more hot coke to form carbon monoxide
CO2(g) + C(s) -> 2CO(g)
What does the carbon monoxide do to the iron oxide?
Reduces (takes oxygen away) the iron oxide to iron
3CO(g) + Fe2O3(s) -> 2Fe(l) + 3CO2(g)
What does limestone do in the blast furnace?
Thermally decomposes and the calcium oxide further reacts with the impurities to form slag
CaCO3(s) -> CaO(s) + CO2(g)
CaO(s) + SiO2(s) -> CaSiO3(s)
Examples of acidic oxides
SO2 and SiO2
Examples of basic oxides
NaOH, KOH and Ca(OH)2
Examples of neutral oxides
N2O, NO, CO
Examples of amphoteric oxides
zinc oxide, aluminum oxide
