JK-TK/Newdata huggingface dataset:
-Water from rivers/lakes. (ii)Chemical processes Ammonia gas is passed up to meet a downward flow of sodium chloride solution / brine to form ammoniated brine/ammoniacal brine mixture in the ammoniated brine chamber The ammoniated brine mixture is then pumped up, atop the carbonator/ solvay tower. In the carbonator/ solvay tower, ammoniated brine/ammoniacal brine mixture slowly trickle down to meet an upward flow of carbon(IV)oxide gas. The carbonator is shelved /packed with quartz/broken glass to (i) reduce the rate of flow of ammoniated brine/ammoniacal brine mixture. (ii)increase surface area of the liquid mixture to ensure a lot of ammoniated brine/ammoniacal brine mixture react with carbon(IV)oxide gas. Insoluble sodium hydrogen carbonate and soluble ammonium chloride are formed from the reaction. Chemical equation CO2(g) + H2O(l) + NaCl (aq) + NH3(g) -> NaHCO3(s) + NH4Cl(aq)
21 The products are then filtered. Insoluble sodium hydrogen carbonate forms the residue while soluble ammonium chloride forms the filtrate. Sodium hydrogen carbonate itself can be used: (i) as baking powder and preservation of some soft drinks. (ii) as a buffer agent and antacid in animal feeds to improve fibre digestion. (iii) making dry chemical fire extinguishers. In the Solvay process Sodium hydrogen carbonate is then heated to form Sodium carbonate/soda ash, water and carbon (IV) oxide gas. Chemical equation 2NaHCO3 (s) -> Na2CO3(s) + CO2(g) + H2O(l) Sodium carbonate is stored ready for use in: (i) during making glass/lowering the melting point of mixture of sand/SiO2 from 1650oC and CaO from 2500oC to around 1500oC (ii) in softening hard water (iii) in the manufacture of soapless detergents. (iv) swimming pool “pH increaser”. Water and carbon(IV)oxide gas are recycled back to the ammoniated brine/ammoniacal brine chamber. More carbon(IV)oxide is produced in the kiln/furnace. Limestone is heated to decompose into Calcium oxide and carbon(IV)oxide.
Water and carbon(IV)oxide gas are recycled back to the ammoniated brine/ammoniacal brine chamber. More carbon(IV)oxide is produced in the kiln/furnace. Limestone is heated to decompose into Calcium oxide and carbon(IV)oxide. Chemical equation CaCO3 (s) -> CaO(s) + CO2(g) Carbon(IV)oxide is recycled to the carbonator/solvay tower. Carbon (IV)oxide is added water in the slaker to form Calcium hydroxide. This process is called slaking. Chemical equation CaO(s) + H2O (l) -> Ca(OH)2 (aq) Calcium hydroxide is mixed with ammonium chloride from the carbonator/solvay tower in the ammonia regeneration chamber to form Calcium chloride , water and more ammonia gas. Chemical equation Ca(OH)2 (aq) +2NH4Cl (aq) -> CaCl2(s) + 2NH3(g) + H2O(l) NH3(g) and H2O(l) are recycled. Calcium chloride may be used: (i)as drying agent in the school laboratory during gas preparation (except ammonia gas)
22 (ii)to lower the melting point of solid sodium chloride / rock salt salts during the Downs process for industrial extraction of sodium metal. Detailed Summary flow diagram of Solvay Process
23 AmmoniatedbrineBrineAmmonia regenerationchamberSolvay Tower/CarbonatorKiln/FurnaceAmmoniumchlorideCarbon(IV)OxideHaberprocessSlakerCalcium hydroxideCalcium oxideWaterSodium hydrogen CarbonateRoasterSodiumcarbonateCalcium chlorideBrine saturated with ammoniaCoke & Limestone
24 Practice 1. The diagram below shows part of the Solvay process used in manufacturing sodium carbonate. Use it to answer the questions that follow. (a)Explain how Sodium Chloride required for this process is obtained from the sea. Sea water is pumped /scooped into shallow pods. Evaporation of most of the water takes place leaving a very concentrated solution. (b)(i) Name process: I. Filtration II.
Evaporation of most of the water takes place leaving a very concentrated solution. (b)(i) Name process: I. Filtration II. Decomposition (ii) Write the equation for the reaction in process: Process I Chemical equation CO2(g) + H2O(l) + NaCl (aq) + NH3(g) -> NaHCO3(s) + NH4Cl(aq) Process II Chemical equation 2NaHCO3 (s) -> Na2CO3(s) + CO2(g) + H2O(l) (c)(i) Name two substances recycled in the solvay process Ammonia gas , Carbon(IV)Oxide and Water. (ii)Which is the by-product of this process? Calcium(II)Chloride /CaCl2 (iii)State two uses that the by-product can be used for: 1. As a drying agent in the school laboratory preparation of gases. 2. In the Downs cell/process for extraction of Sodium to lower the melting point of rock salt. Carbon (IV)oxide Ammonium chloride Process I Saturated sodium chloride solution Ammonia Sodium hydrogen carbonate Process II Sodium carbonate
25 (iv)Write the chemical equation for the formation of the byproducts in the Solvay process. Chemical equation Ca(OH)2 (aq) +2NH4Cl (aq) -> CaCl2(s) + 2NH3(g) + H2O(l) (d)In an experiment to determine the % purity of Sodium carbonate produced in the Solvay process ,2.15g of the sample reacted with exactly 40.0cm3 of 0.5M Sulphuric(VI)acid. (i)Calculate the number of moles of sodium carbonate that reacted. Chemical equation Na2CO3 (aq) +H2SO4 (aq) -> Na2SO4 (aq)+ CO2(g) + H2O(l) Mole ratio Na2CO3 :H2SO4 => 1:1 Moles H2SO4 = Molarity x Volume => 0.5 x 40.0 = 0.02 Moles 1000 1000 Moles of Na2CO3 = 0.02 Moles (ii)Determine the % of sodium carbonate in the sample.
Chemical equation Ca(OH)2 (aq) +2NH4Cl (aq) -> CaCl2(s) + 2NH3(g) + H2O(l) (d)In an experiment to determine the % purity of Sodium carbonate produced in the Solvay process ,2.15g of the sample reacted with exactly 40.0cm3 of 0.5M Sulphuric(VI)acid. (i)Calculate the number of moles of sodium carbonate that reacted. Chemical equation Na2CO3 (aq) +H2SO4 (aq) -> Na2SO4 (aq)+ CO2(g) + H2O(l) Mole ratio Na2CO3 :H2SO4 => 1:1 Moles H2SO4 = Molarity x Volume => 0.5 x 40.0 = 0.02 Moles 1000 1000 Moles of Na2CO3 = 0.02 Moles (ii)Determine the % of sodium carbonate in the sample. Molar mass of Na2CO3 = 106g Mass of Na2CO3 = moles x Molar mass => 0.02 x 106 = 2.12 g % of Na2CO3 = ( 2.12 g x 100) = 98.6047% 2.15 (e) State two uses of soda ash. (i) during making glass/lowering the melting point of mixture of sand/SiO2 from 1650oC and CaO from 2500oC to around 1500oC (ii) in softening hard water (iii) in the manufacture of soapless detergents. (iv) swimming pool “pH increaser”. (f)The diagram below shows a simple ammonia soda tower used in manufacturing sodium carbonate .Use it to answer the questions that follow: Raw materialExcess Carbon(IV)oxide Metal plates Substance
26 (i)Name the raw materials needed in the above process -Ammonia -Water -Carbon(IV)oxide -Limestone -Brine/ Concentrated sodium chloride (ii)Identify substance A Ammonium chloride /NH4Cl (iii) Write the equation for the reaction taking place in: I.Tower.
(i) during making glass/lowering the melting point of mixture of sand/SiO2 from 1650oC and CaO from 2500oC to around 1500oC (ii) in softening hard water (iii) in the manufacture of soapless detergents. (iv) swimming pool “pH increaser”. (f)The diagram below shows a simple ammonia soda tower used in manufacturing sodium carbonate .Use it to answer the questions that follow: Raw materialExcess Carbon(IV)oxide Metal plates Substance
26 (i)Name the raw materials needed in the above process -Ammonia -Water -Carbon(IV)oxide -Limestone -Brine/ Concentrated sodium chloride (ii)Identify substance A Ammonium chloride /NH4Cl (iii) Write the equation for the reaction taking place in: I.Tower. Chemical equation CO2(g) + NaCl (aq) + H2O(l) + NH3(g) -> NaHCO3(s) + NH4Cl(aq) II. Production of excess carbon (IV)oxide. Chemical equation CaCO3 (s) -> CaO(s) + CO2(g) III. The regeneration of ammonia Chemical equation Ca(OH)2 (aq) +2NH4Cl (aq) -> CaCl2(s) + 2NH3(g) + H2O(l) (iv)Give a reason for having the circular metal plates in the tower. -To slow the downward flow of brine. -To increase the rate of dissolving of ammonia. -To increase the surface area for dissolution (v)Name the gases recycled in the process illustrated above. Ammonia gas , Carbon(IV)Oxide and Water. 2. Describe how you would differentiate between carbon (IV)oxide and carbon(II)oxide using chemical method. Method I -Bubble both gases in lime water/Ca(OH)2 -white precipitate is formed if the gas is carbon (IV) oxide - No white precipitate is formed if the gas is carbon (II) oxide Method II
27 -ignite both gases - Carbon (IV) oxide does not burn/ignite - Carbon (II) oxide burn with a blue non-sooty flame. Method III -Lower a burning splint into a gas containing each gas separately.
Describe how you would differentiate between carbon (IV)oxide and carbon(II)oxide using chemical method. Method I -Bubble both gases in lime water/Ca(OH)2 -white precipitate is formed if the gas is carbon (IV) oxide - No white precipitate is formed if the gas is carbon (II) oxide Method II
27 -ignite both gases - Carbon (IV) oxide does not burn/ignite - Carbon (II) oxide burn with a blue non-sooty flame. Method III -Lower a burning splint into a gas containing each gas separately. -burning splint is extinguished if the gas is carbon (IV) oxide -burning splint is not extinguished if the gas is carbon (II) oxide. 3.Using Magnesium sulphate(VI)solution ,describe how you can differentiate between a solution of sodium carbonate from a solution of sodium hydrogen carbonate -Add Magnesium sulphate(VI) solution to separate portions of a solution of sodium carbonate and sodium hydrogen carbonate in separate test tubes -White precipitate is formed in test tube containing sodium carbonate -No white precipitate is formed in test tube containing sodium hydrogen carbonate. Chemical equation Na2CO3 (aq) +MgSO4 (aq) -> Na2SO4 (aq) + MgCO3(s) (white ppt) Ionic equation CO32- (aq) + Mg2+ (aq) -> MgCO3(s) (white ppt) Chemical equation 2NaHCO3 (aq) +MgSO4 (aq) -> Na2SO4 (aq) + Mg(HCO3)2 (aq) (colourless solution) 4. The diagram below shows a common charcoal burner .Assume the burning take place in a room with sufficient supply of air. (a)Explain what happens around:
28 (i)Layer A Sufficient/excess air /oxygen enter through the air holes into the burner .It reacts with/oxidizes Carbon to carbon(IV)oxide Chemical equation C(s) + O2(g) -> CO2 (g) (ii)Layer B Hot carbon(IV)oxide rises up and is reduced by more carbon/charcoal to carbon (II)oxide. Chemical equation C(s) + CO2(g) -> 2CO (g) (ii)Layer C Hot carbon(II)oxide rises up and burns with a blue flame to be oxidized by the excess air to form carbon(IV)oxide.
The diagram below shows a common charcoal burner .Assume the burning take place in a room with sufficient supply of air. (a)Explain what happens around:
28 (i)Layer A Sufficient/excess air /oxygen enter through the air holes into the burner .It reacts with/oxidizes Carbon to carbon(IV)oxide Chemical equation C(s) + O2(g) -> CO2 (g) (ii)Layer B Hot carbon(IV)oxide rises up and is reduced by more carbon/charcoal to carbon (II)oxide. Chemical equation C(s) + CO2(g) -> 2CO (g) (ii)Layer C Hot carbon(II)oxide rises up and burns with a blue flame to be oxidized by the excess air to form carbon(IV)oxide. 2CO (g) + O2(g) -> 2CO2(g) (b)State and explain what would happen if the burner is put in an enclosed room. The hot poisonous /toxic carbon(II)oxide rising up will not be oxidized to Carbon(IV)oxide. (c)Using a chemical test , describe how you would differentiate two unlabelled black solids suspected to be charcoal and copper(II)oxide. Method I -Burn/Ignite the two substances separately. -Charcoal burns with a blue flame - Copper(II)oxide does not burn Method II -Add dilute sulphuric(VI)acid/Nitric(V)acid/Hydrochloric acid separately. -Charcoal does not dissolve. - Copper(II)oxide dissolves to form a colourless solution. 5. Excess Carbon(II)oxide was passed over heated copper(II)oxide as in the set up shown below for five minutes. 29 Dry carbon(IV)oxideHEATCopper(II)oxideBlue flame A (a)State and explain the observations made in the combustion tube. Observation Colour change from black to brown Explanation Carbon (II)oxide reduces black copper(II)oxide to brown copper metal itself oxidized to Carbon(IV)oxide. Chemical equation CO(g) + CuO (s) -> Cu(s) + CO2(g) (black) (brown) (b) (i)Name the gas producing flame A Carbon(II)oxide (ii)Why should the gas be burnt?
29 Dry carbon(IV)oxideHEATCopper(II)oxideBlue flame A (a)State and explain the observations made in the combustion tube. Observation Colour change from black to brown Explanation Carbon (II)oxide reduces black copper(II)oxide to brown copper metal itself oxidized to Carbon(IV)oxide. Chemical equation CO(g) + CuO (s) -> Cu(s) + CO2(g) (black) (brown) (b) (i)Name the gas producing flame A Carbon(II)oxide (ii)Why should the gas be burnt? It is toxic/poisonous (iii)Write the chemical equation for the production of flame A 2CO(g) + O2(g) -> 2CO2(g) (c)State and explain what happens when carbon(IV)oxide is prepared using Barium carbonate and dilute sulphuric(VI)acid. Reaction starts then stops after sometime producing small/little quantity of carbon(IV)oxide gas. Barium carbonate react with dilute sulphuric(VI)acid to form insoluble Barium sulphate(VI) that cover/coat unreacted Barium carbonate stopping further reaction to produce more Carbon(IV)oxide. 30 (d) Using dot () and cross(x) to represent electrons show the bonding in a molecule of : (i) Carbon(II)oxide jgthungu@gmail.com56x●xxOxxCx ●●●lone pairs of electrons in carbon and oxygen atoms6 bonded pairs of electrons2covalent bonds1 dative bond (ii) Carbon(IV)Oxide. jgthungu@gmail.com30●x O●●C●x●x●xlone pairs of electrons in oxygen atom4 bonded pairs of electronsO●●●●●●CO2 (triatomic molecule) (e) Carbon (IV)oxide is an environmental pollutant of global concern. Explain. -It is a green house gas thus causes global warming. -It dissolves in water to form acidic carbonic acid which causes “acid rain” (f)Explain using chemical equation why lime water is used to test for the presence of Carbon (IV) oxide instead of sodium hydroxide.
Explain. -It is a green house gas thus causes global warming. -It dissolves in water to form acidic carbonic acid which causes “acid rain” (f)Explain using chemical equation why lime water is used to test for the presence of Carbon (IV) oxide instead of sodium hydroxide. 31 Using lime water/calcium hydroxide: - a visible white precipitate of calcium carbonate is formed that dissolves on bubbling excess Carbon (IV) oxide gas Chemical equation Ca(OH)2(aq) + CO2 (g) -> CaCO3 (s) + H2O(l) (white precipitate) CaCO3 (aq) + H2O(l) + CO2 (g) -> Ca(HCO3) 2 (aq) Using sodium hydroxide: - No precipitate of sodium carbonate is formed Both sodium carbonate and sodium hydrogen carbonate are soluble salts/dissolves. Chemical equation 2NaOH (aq) + CO2 (g) -> Na2CO3 (s) + H2O(l) (No white precipitate) Na2CO3 (s) + H2O(l) + CO2 (g) -> 2NaHCO3 (s) (g)Ethan-1,2-dioic acid and methanoic acid may be used to prepare small amount of carbon(II)oxide in a school laboratory. (i) Explain the modification in the set up when using one over the other. Before carbon(II)oxide is collected: -when using methanoic acid, no concentrated sodium/potassium hydroxide is needed to absorb Carbon(IV)oxide. -when using ethan-1,2-dioic acid, concentrated sodium/potassium hydroxide is needed to absorb Carbon(IV)oxide. (ii)Write the equation for the reaction for the formation of carbon(II)oxide from: I.Methanoic acid. Chemical equation HCOOH(aq) -> CO(g) + H2O(l) II. Ethan-1,2-dioic acid Chemical equation HOOCCOOH(aq) -> CO2(g)+CO(g)+H2O(l) (h)Both carbon(II)oxide and carbon(IV)oxide affect the environment. Explain why carbon(II)oxide is more toxic/poisonous. -Both gases are colourless,denser than water and odourless.
Ethan-1,2-dioic acid Chemical equation HOOCCOOH(aq) -> CO2(g)+CO(g)+H2O(l) (h)Both carbon(II)oxide and carbon(IV)oxide affect the environment.

Explain why carbon(II)oxide is more toxic/poisonous.

-Both gases are colourless,denser than water and odourless.

-Carbon(II)oxide is preferentially absorbed by human/mammalian haemoglobin when inhaled forming stable carboxyhaemoglobin instead of oxyhaemoglobin.This reduces the free haemoglobin in the blood leading to suffocation and quick death.

-Carbon(IV)oxide is a green house gas that increases global warming.

-Carbon(II)oxide is readily oxidized to carbon(IV)oxide 6.Study the flow chart below and use it to answer the questions that follow.

32 (a)Name: (i)the white precipitate A Calcium carbonate (ii) solution B Calcium hydrogen carbonate (iii) gas C Carbon(IV)oxide (iv) white residue B Calcium oxide (v) solution D Calcium hydroxide/lime water (b)Write a balanced chemical equation for the reaction for the formation of: (i) the white precipitate A from solution D Chemical equation Ca(OH)2(aq) + CO2 (g) -> CaCO3 (s) + H2O(l) (ii) the white precipitate A from solution B Chemical equation Ca(HCO3)2(aq) -> CO2 (g) + CaCO3 (s) + H2O(l) (iii) solution B from the white precipitate A Chemical equation CO2 (g) + CaCO3 (s) + H2O(l) -> Ca(HCO3)2(aq)
33 (iv) white residue B from the white precipitate A Chemical equation CaCO3(s) -> CO2 (g) + CaO (s) (iv) reaction of white residue B with water Chemical equation CaO (s) + H2O(l) -> Ca(OH)2(aq)
PRACTICAL CHEMISTRY
Introduction
Scientific subjects are, by their nature, experimental. It is accordingly important that an assessment of a student’s knowledge and understanding of Chemistry should contain a component relating to practical work and experimental skills. This booklet has been produced to help students preparing for and taking practical Examinations. The material contained in this booklet does not extend the curriculum specification content. Rather it seeks to help the candidate succeed in practical examination by explaining in more depth what is required of him or her in carrying out the exercises, making observations and measurements with appropriate precision and recording these methodically. This booklet advices candidate on how he or she should interpret, explain, evaluate and communicate the results of the exercises clearly and logically using relevant chemical knowledge and understanding and using appropriate specialist vocabulary. 1.1APPARATUS IN A CHEMISTRY LABORATORY
1.2 SPECIAL LABORATORY APPARATUS AND TECHNIQUES
(a) USING THE BURETTE
A burette is used to deliver solution in precisely measured, variable volumes. Burettes are used primarily for titration, to deliver one reactant until the precise end point of the reaction is reached. To fill a burette, close the stopcock at the bottom and use a funnel. You may need to lift up on the funnel slightly, to allow the solution to flow in freely. You can also fill a burette using a disposable transfer pipette. This works better than a funnel for the small, 10 mL burettes. Be sure the transfer pipette is dry or conditioned with the titrant, so the concentration of solution will not be changed. Before titrating, condition the burette with titrant solution and check that the burette is flowing freely. To condition a piece of glassware, rinse it so that all surfaces are coated with solution, then drain. Conditioning two or three times will insure that a stray drop of water does not change the concentration of titrant.Rinse the tip of the burette with water from a wash bottle and dry it carefully. After a minute, check for solution on the tip to see if your burette is leaking. The tip should be clean and dry before you take an initial volume reading.When your burette is conditioned and filled, with no air bubbles or leaks, take an initial volume reading. A burette-reading card with a black rectangle can help you to take a more accurate reading. Read the bottom of the meniscus.
The tip should be clean and dry before you take an initial volume reading.When your burette is conditioned and filled, with no air bubbles or leaks, take an initial volume reading. A burette-reading card with a black rectangle can help you to take a more accurate reading. Read the bottom of the meniscus. Be sure your eye is at the level of meniscus, not above or below. Reading from an angle, rather than straight on, results in a parallax error. Deliver solution to the titration flask by turning the stopcock. The solution should be delivered quickly until a couple of mL from the endpoint. The endpoint should be approached slowly, a drop at a time. Use a wash bottle to rinse the tip of the burette and the sides of the flask. Your TA can show you how to deliver a partial drop of solution, when near the endpoint. (b) Volumetric (measuring) Flasks
Erlenmeyer flasks and beakers are used for mixing, transporting, and reacting, but not for accurate measurements. The volumes stamped on the sides are approximate and accurate to within about 5%. (c) Graduated Cylinders
Graduated cylinders are useful for measuring liquid volumes to within about 1%. They are for general-purpose use, but not for quantitative analysis. If greater accuracy is needed, use a pipette or volumetric flask. (d) Pipette
A pipette is used to measure small amounts of solution very accurately. A pipette bulb is used to draw solution into the pipette. Start by squeezing the bulb in your preferred hand. Then place the bulb on the flat end of the pipette.Place the tip of the pipette in the solution and release your grip on the bulb to pull solution into the pipette. Draw solution in above the mark on the neck of the pipette. If the volume of the pipette is larger than the volume of the pipette bulb, you may need to remove the bulb from the pipette and squeeze it and replace it on the pipette a second time, to fill the pipette volume completely. Quickly, remove the pipette bulb and put your index finger on the end of the pipette. Gently release the seal made by your finger until the level of the solution meniscus exactly lines up with the mark on the pipette. Practice this with water until you are able to use the pipette and bulb consistently and accurately.
Quickly, remove the pipette bulb and put your index finger on the end of the pipette. Gently release the seal made by your finger until the level of the solution meniscus exactly lines up with the mark on the pipette. Practice this with water until you are able to use the pipette and bulb consistently and accurately. (e) Volumetric Flask
A volumetric flask is used to make up a solution of fixed volume very accurately. This volumetric flask measures 500 mL ± 0.2 mL. This is a relative uncertainty of 4 x 10-4 or 400 parts per million. To make up a solution, first dissolve the solid material completely, in less water than required to fill the flask to the mark. After the solid is completely dissolved, very carefully fill the flask to the 500 mL mark. Move your eye to the level of the mark on the neck of the flask and line it up so that the circle around the neck looks like a line, not an ellipse. Then add distilled water a drop at a time until the bottom of the meniscus lines up exactly with the mark on the neck of the flask. Take care that no drops of liquid are in the neck of the flask above the mark. After the final dilution, remember to mix your solution thoroughly, by inverting the flask and shaking. (f) Analytical Balance
An analytical balance measures masses to within 0.0001 g. Use these balances when you need this high degree of precision.Turn the balance on by pressing the control bar. The display lights up for several seconds, then resets to 0.0000.Place creased, small weighing paper on the balance pan.Close the sliding glass doors. Wait for the green dot on the left to go out. This is the stability indicator light, indicating that the weight is stable.Press the control bar to cancel out the weight of the container or paper. The display will again read 0.0000. Carefully add the substance to be weighed up to the desired mass. Do not attempt to reach a particular mass exactly. Before recording the mass, close the glass doors and wait until the stability detector lamp goes out. Record mass of solid. Don't pick up tare containers with bare hands since your fingerprints add mass. Use tongs to prevent this.Don't lean on the bench while weighing.Do record the mass of your container, if you will need it later.Do check the level indicator bubble before weighing.