RPs Flashcards
Making a Soluble Salt
Warm 50 cm³ of dilute acid in a beaker on a Bunsen burner.
Add insoluble oxide/base until in excess (no more dissolves).
Filter to remove excess base; collect filtrate in an evaporating basin.
Heat gently to evaporate water until saturated (test with cold glass rod for crystals).
Leave to crystallize; decant excess liquid and dry crystals.
Titration
Pipette 25 cm³ of alkali into a conical flask; add 2–3 drops of indicator (e.g., methyl orange).
Fill burette with acid (rinse first with acid).
Titrate acid into alkali until endpoint (color change is from yellow to orange).
Repeat until concordant results (±0.1 cm³); calculate mean volume.
Electrolysis
Method:
Pour 50 cm³ copper chloride solution into a beaker with electrodes (carbon/graphite).
Connect to DC power supply (4V); observe electrodes for 5 minutes.
Test gas at anode with damp litmus paper (chlorine bleaches it).
Observe copper deposit at cathode (pinkish metal)
Temperature Change
Method(Neutralisation):
Measure 25 cm³ of HCl into a polystyrene cup (calorimeter).
Record initial temperature.
Add 5 cm³ NaOH; stir and record highest temperature.
Repeat experiment, adding NaOH in 5 cm³ increments.
Plot graph of temperature vs. volume; identify neutralization point.
Method(Metal+Acid):
Place the polystyrene cup inside the glass beaker to make it more stable.
Measure an appropriate volume of the solution, eg 25 cm3.
Measure an appropriate mass of the solid, or select a suitable sized piece of metal.
Place the solution in a polystyrene cup.
Record the temperature of the solution.
Add the solid and record the highest or lowest temperature obtained.
Change your independent variable and repeat the experiment. Your independent variable could be the surface area of the solid, or the type of acid being used, or the type of metal being used.
Controls:Same Concentrations and Insulation
Rate of Reaction
Method A (Gas Volume):
React magnesium with HCl; collect gas in syringe.
Record volume at regular intervals; plot volume vs. time.
Method B (Sodium Thiosulfate):
Mix Na₂S₂O₃ with HCl in a flask over a cross.
Time how long until cross disappears.
Plot 1/time vs. concentration to show rate.
Repeat experiments with different concentrations of HCL and record the time taken
Variables:
Independent: Concentration/temperature.
Dependent: Time/gas volume.
Control:Volume of Thiosulfate
Chromatography
Method:
Draw pencil line 2 cm from chromatography paper edge.
Spot food dyes (A–D) and unknown (U).
Suspend paper in beaker and pour solvent(water) so it starts at the pencil line while clipping paper to the top of the beaker; allow solvent to rise 3/4 of the paper.
Remove paper and draw line with pencil close to the wet edge(solvent front line) when dried.
Measure distances between solvent front and first pencil line.This is solvent distance
Measure distance travelled by solutes(dye)
find Rf value by dividing dye distance/solvent distance
Gas Tests
Hydrogen: Burning splint → squeaky pop.
Oxygen: Glowing splint relights.
CO₂: Turns limewater cloudy when bubbled using a delivery tube.
Chlorine: Bleaches damp litmus paper.
Ion Tests
Flame Tests:
Li⁺: Crimson.
Na⁺: Yellow.
K⁺: Lilac
Cu²⁺: Green
Ca²⁺: Orange red
Precipitation with NaOH:
Cu²⁺: Blue precipitate.
Fe²⁺: Green; Fe³⁺: Brown.
Al³⁺:White
Mg²⁺:White
Ca²⁺:White
If it dissolves in excess NaOH solution it is aluminium ions and if it doesnt show a green flame in the flame test it is magnesium ions
Carbonates:
Carbonates react with acids to release carbon dioxide which can be identified using the carbon dioxide test(LIMEWATER)
Sulfates:
To test for sulfate ions:
add a few drops of dilute hydrochloric acid to the sample add a few drop of dilute barium chloride solution
A white precipitate forms if sulfate ions are present.
Halides:
To test for halide ions:
add a few drops of dilute nitric acid to the sample
add a few drop of dilute silver nitrate solution
Observe the colour
Cl⁻: White precipitate.
Br⁻: Cream
I⁻: Yellow.
Water Analysis and Purification
Method(Analysis):
Check pH using universal indicator, if pH is not 7 the water is not pure. There may still be dissolved solids
Record mass of evaporating basin and place water sample on it and heat gently over a Bunsen burner tripod and gauze. Wait until all the water is evaporated.
Then measure the basin, if it has increased in mass then solids have formed on the basin. There should be crystals as well formed on the basin.
Method(Purification)
Using a still, heat water which evaporates and condenses in a condenser and empties out into another beaker as distilled water which is pure water and contains no dissolved solids or acids and alkalis.
