practicles Flashcards
(98 cards)
1
Q
Preparation of copper sulfate crystals
A
React sulfuric acid with excess copper oxide
2
Q
Chemical equation for CuO and H2SO4
A
CuO + H2SO4 → CuSO4 + H2O
3
Q
Safety precautions for preparing salts
A
Bunsen burner should be turned off or put on the safety flame when not in use; sulfuric acid is corrosive so wear eye protection.
4
Q
Methods of separating mixtures
A
Filtration and Crystallisation.
5
Q
Separating insoluble product from solution
A
Use filtration: filter paper placed in a funnel over a conical flask
6
Q
Separating soluble solids from solutions
A
Use evaporation: place the mixture in an evaporating dish
7
Q
Separating soluble solid that decomposes when heated
A
Use crystallisation: pour the solution into an evaporating dish and heat gently
8
Q
Volume of sulfuric acid to neutralise NaOH
A
Place exactly 25cm3 of sodium hydroxide in a conical flask on a white tile
9
Q
Apparatus for titration
A
Burette
10
Q
Purpose of white tile in titration
A
The white tile is placed under the reacting mixture
11
Q
Volumetric pipette vs measuring cylinder
A
A volumetric pipette will measure 25cm3 more accurately so it is usually used for titrations.
12
Q
Purpose of repeating a titration
A
To allow a mean titre to be calculated
13
Q
Colour of phenolphthalein in acid
A
Phenolphthalein is colourless in acid.
14
Q
Colour of phenolphthalein in alkali
A
Phenolphthalein is pink in alkali.
15
Q
Acid
A
colourless
16
Q
Alkali
A
pink
17
Q
Rough trial in titration
A
The first trial gives an approximate idea of where the end point is so then for further titres you can be more precise as you know approximately what volume will be required for neutralisation.
18
Q
Safety precautions in titration
A
- Wear eyewear and be aware of the dangers of the chemicals used
19
Q
Burettes in titrations
A
Burettes allow the solution to be added drop by drop in very small quantities.
20
Q
Methyl Orange
A
Red (acid) to yellow (alkali)
21
Q
Litmus Blue
A
Red (acid) to blue (alkali)
22
Q
Calculating acid concentration from alkali
A
- Calculate the number of moles of the alkali using the known volume and concentration. - Use the chemical equation to work out the ratio of acid and alkali that react and hence work out how many mole of acid have reacted. - Divide the moles of acid by the volume used in neutralisation.
23
Q
Converting acid concentration to g/dm3
A
Multiply the concentration in mol/dm3 by the molar mass (Mr) of the acid to give the value in g/dm3.
24
Q
Setting up electrolysis experiment
A
- Place the positive and negative electrodes in a beaker containing a molten or dissolved ionic compound. - Connect both electrodes to a power supply with wires.
25
Investigating CuCl2 electrolysis
- Half fill a beaker with aqueous CuCl2. - Place a lid on the beaker and insert the electrodes into the solution through holes in the lid (electrodes must not touch). - Connect the electrodes to a low voltage power supply. - Switch the power supply on to 4V. - Turn off the power after a few minutes and record any observations.
26
Products at cathode and anode in electrolysis
Cathode: Metals or hydrogen; Anode: Non-metals.
27
Observations at electrodes for CuCl2 electrolysis
Positive electrode: Bubbles of gas (chlorine); Negative electrode: Electrode coated with a brown solid (copper).
28
Observations at electrodes for NaCl electrolysis
Positive electrode: Bubbles of gas (chlorine); Negative electrode: Bubbles of gas rapidly produced (hydrogen).
29
Diagram of CuCl2 electrolysis apparatus
Draw a diagram of the apparatus set up when copper chloride solution is electrolysed.
30
Replacing the positive electrode
Why must the positive electrode (anode) be regularly replaced?
31
Positive electrode
Made of carbon and reacts with oxygen to produce carbon dioxide.
32
Half equation for CuCl2 at cathode
Cu2+ + 2e- → Cu
33
Half equation for CuCl2 at anode
2Cl- → Cl2 + 2e-
34
Half equation for NaCl at cathode
2H+ + 2e- → H2
35
Half equation for NaCl at anode
2Cl- → Cl2 + 2e-
36
Reason sodium is not produced in NaCl electrolysis
Hydrogen is produced because sodium is more reactive than hydrogen. Sodium remains in the solution.
37
Test for chlorine gas
The gas produced will bleach damp litmus paper - it will turn white.
38
Test for hydrogen gas
The gas produced will make a squeaky pop with a lighted splint.
39
Test for oxygen gas
The gas produced will relight a glowing splint.
40
Investigating temperature change with NaOH and HCl
- Measure 25cm3 of HCl into a polystyrene cup - Measure the starting temperature of HCl - Add 5cm3 of NaOH to the cup - Then stir the mixture and measure the maximum temperature reached. Record it in a table - Repeat the experiment with increasing volumes of NaOH: 10cm3
41
Difference in calculated energy values
Energy gets lost to the surroundings.
42
Exothermic reaction temperature change
The thermometer will record an increase in temperature as energy will have been transferred to the surroundings.
43
Reducing heat energy loss
- Mix the reactants in a polystyrene cup - Place the polystyrene cup in a beaker of cotton wool - Lid on the cup to reduce energy lost by evaporation.
44
Starting temperature for chemicals
They need to be the same temperature so that their individual temperatures do not have an effect on the temperature recorded once combined.
45
Ensuring same starting temperature in test tubes
Place the test tubes in a water bath at 25oC. Use a thermometer to ensure the reactants are the same temperature.
46
Importance of stirring during temperature reading
To ensure the temperature measured is consistent throughout the mixture. To ensure the reactants have fully reacted.
47
Endothermic or exothermic reaction with temperature decrease
The reaction is endothermic.
48
Digital thermometer
A device used to measure temperature more precisely.
49
Mean temperature measurement
An average temperature calculated by repeating the experiment.
50
Neutralisation reaction
A chemical reaction between an acid and an alkali that produces salt and water.
51
Temperature change calculation
The difference between the initial and final temperatures recorded during the reaction.
52
Controlled variables in neutralisation
Factors that must remain constant
53
Reaction completion indicators
Mass of reaction mixture
54
Rate of reaction measurement methods
Observing precipitate formation
55
Rate of reaction formula
Rate of Reaction = Amount of product formed or reactant used / Time.
56
Precipitate rate measurement
Observing a black cross through a solution until it disappears.
57
Colour change rate measurement
Timing how long it takes for reactants to turn colourless.
58
Subjectivity in precipitate experiments
Variability in human perception of when a mark disappears or colour changes.
59
Mass change rate measurement
Using a mass balance to measure initial mass
60
Gas production rate measurement
Using a gas syringe attached to a conical flask to measure gas volume produced.
61
Rate of reaction after 30 seconds
Plotting results on a graph and calculating the gradient of the tangent at 30 seconds.
62
Units of rate of reaction (mass change)
Measured in grams per second (g/s).
63
Units of rate of reaction (gas volume)
Measured in cubic centimeters per second (cm3/s).
64
HCl concentration effect on reaction rate
Investigating how varying hydrochloric acid concentration affects the rate of reaction with magnesium.
65
HCl concentration effect on magnesium reaction
Investigate how HCl concentration affects the rate of reaction when magnesium is added by measuring the volume of gas produced.
66
Sodium thiosulfate concentration effect on HCl reaction
Investigate how sodium thiosulfate concentration affects the rate of reaction with HCl by measuring the time it takes to cover a cross.
67
Flame test procedure
Clean a platinum wire loop by dipping it in HCl and holding it in a blue flame until it burns without color
68
Precautions for Bunsen burner use
Don't leave unattended
69
Flame test result for lithium ions
Lithium ions (Li+): Crimson flame.
70
Flame test result for sodium ions
Sodium ions (Na+): Yellow flame.
71
Flame test result for potassium ions
Potassium ions (K+): Lilac flame.
72
Flame test result for calcium ions
Calcium ions (Ca2+): Orange-red flame.
73
Flame test result for copper ions
Copper ions (Cu2+): Green flame.
74
Wire cleaning necessity before flame test
To remove any unwanted ions that might obscure the color of the flame.
75
Flame test limitation with mixed metal ions
The flame colors of some ions may be hidden by the colors of other metal ions.
76
Testing for carbonate ions
Add a few drops of HCl to the sample in a test tube
77
Chemical equation for HCl and Na2CO3 reaction
Na2CO3 + 2HCl → CO2 + 2NaCl + H2O.
78
Testing for sulfate ions
Add HCl to remove any CO3^2- ions
79
Chemical equation for BaCl2 and MgSO4 reaction
BaCl2 + MgSO4 → BaSO4 + MgCl2. BaSO4 is a white precipitate.
80
Testing for halide ions
Procedure to carry out a test for halide ions.
81
Nitric Acid Reaction
Add a couple of drops of nitric acid to react with any carbonate ions which might obscure the experiment.
82
Silver Nitrate and Chloride
What colour precipitate is formed when silver nitrate is added to a chloride solution? White precipitate of silver chloride.
83
Silver Nitrate and Bromide
What colour precipitate is formed when silver nitrate is added to a bromide solution? Cream precipitate of silver bromide.
84
Silver Nitrate and Iodide
What colour precipitate is formed when silver nitrate is added to an iodide solution? Yellow precipitate of silver iodide.
85
Sodium Hydroxide and Calcium
What colour precipitate forms when sodium hydroxide reacts with calcium ions? White precipitate.
86
Sodium Hydroxide and Copper(II)
What colour precipitate forms when sodium hydroxide reacts with copper(II) ions? Blue precipitate.
87
Sodium Hydroxide and Iron(II)
What colour precipitate forms when sodium hydroxide reacts with iron(II) ions? Green precipitate.
88
Sodium Hydroxide and Iron(III)
What colour precipitate forms when sodium hydroxide reacts with iron(III) ions? Brown precipitate.
89
Sodium Hydroxide and Aluminium
What colour precipitate forms when sodium hydroxide reacts with aluminium ions? White precipitate at first. Redissolves with excess NaOH to form a colourless solution.
90
Sodium Hydroxide and Magnesium
What colour precipitate forms when sodium hydroxide reacts with magnesium ions? White precipitate.
91
Identifying Aluminium and Magnesium
Given two solutions
92
Testing pH of Water
How can you test the pH of a sample of water? Use universal indicator paper or a digital pH probe.
93
pH of Pure Water
What would you expect the pH of a sample of pure water to be? What colour would this be on universal indicator paper? pH 7 - green.
94
Finding Mass of Salt in Water
How could you find the mass of salt dissolved in a sample of water? Weigh an empty evaporating basin
95
Purifying Water
State how can you purify a sample of water. Distillation.
96
Water Purification by Distillation
Describe how a sample of water can be purified by distillation. First test the pH. Add acid/alkali as necessary to obtain pH 7. Place the water sample in a conical flask and connect the flask to distillation apparatus (including a condenser). As the water in the flask is heated
97
Testing Purity of Distilled Water
How could you test that the water collected from a distillation experiment is pure water? Check the pH is still pH 7. Determine the boiling point and check it matches that of water (100oC).
98
Safety Precautions in Water Purification
What safety precautions need to be considered when purifying water? Bunsen burner turned off or put on safety flame when not in use
