Practicals Flashcards
Describe a method to make pure, dry crystals of magnesium sulfate from a metal oxide and a dilute acid
- Add sulfuric acid to a beaker
- Warm sulfuric acid
- Add metal oxide and stir
- Continue adding metal oxide until it is in excess
- Filter out excess metal oxide using filter paper and a funnel
- Heat solution in an evaporating basin to crystallisation point
- Leave in a cool place to crystallise
- Pat dry with filter paper
Plan an experiment to investigate temperature change
- Place a polystyrene cup in a beaker
- Use a measuring cylinder to put 25cm³ of dilute hydrochloric acid into the cup
- Place a lid on the cup and make a hole in it
- Place the thermometer into the hole and record the starting temperature
- Use the measuring cylinder to put 5cm³ of sodium hydroxide into the cup
- Swirl the solution using the thermometer
- Record the highest temperature reached
- Repeat experiment several times, increasing volume of sodium hydroxide by 5cm³ each time until it reaches 40cm³
Give one independent variable in the temperature change experiment
Volume of sodium hydroxide solution
Give one control variable in the temperature change experiment
Volume of hydrochloric acid
Give one dependent variable in the temperature change experiment
Temperature change
Plan an experiment to investigate how the concentration of a reactant affects the rate of reaction (disappearing cross experiment)
- Use a measuring cylinder to put 10 cm³ of sodium thiosulfate into a conical flask
- Place the conical flask onto a printed black cross
- Add 10cm³ of hydrochloric acid to the conical flask
- Swirl solution and start a stopwatch
- Look down through the top of the flask
- Stop the clock when the cross can no longer be seen
- Repeat experiment using different concentrations of sodium thiosulfate
Plan an experiment to investigate how the concentration of a reactant affects the rate of reaction (volume of gas released)
- Use a measuring cylinder to put 50cm³ of hydrochloric acid into a conical flask
- Connect the bung and delivery tube to the flask
- Connect the tube to the gas syringe/upside down measuring cylinder
- Add a 3cm piece of magnesium ribbon to the flask
- Start a stopwatch
- Record the volume of hydrogen gas collected every 10 seconds
- Continue until no more hydrogen is given off
- Repeat experiment with different concentrations of hydrochloric acid
Write a method for chromatography
- Draw pencil start line on chromatography paper
- Place spot of [mixture] on start line
- Place [solvent] in a beaker
- Place chromatography paper in solvent
–> [solvent] should be below start line - Use a lid
- Wait for solvent to travel up chromatography paper
- Mark solvent front
- Dry the chromatography paper
Write a method for a flame test
- Clean wire (using HCl)
- Dip wire into unknown compound
- Place in roaring (blue) flame
- Observe the colour
Name the 5 metal compounds that can be detected through flame tests
- Lithium
- Sodium
- Potassium
- Calcium
- Copper
(LSPCC)
Name the colour produced from a positive lithium flame test
Crimson
Name the colour produced from a positive sodium flame test
Yellow
Name the colour produced from a positive potassium flame test
Lilac
Name the colour produced from a positive calcium flame test
Orange-red
Name the colour produced from a positive copper flame test
Green
Write a method to test for carbonate ions, including the positive result
- Put carbonate into a test tube
- Add dilute hydrochloric acid
- Bubble through limewater
—> Limewater turns cloudy
Give the positive result for a carbonate ion test
Limewater turns cloudy
Write a method to test for halide ions
- Add halide to test tube
- Add nitric acid
- Add silver nitrate solution
Give the result for a positive chloride test
White precipitate
Give the result for a positive bromide test
Cream precipitate
Give the result for a positive iodide test
Yellow precipitate
Outline the purpose of chromatography
Separate mixtures into their components and identify them
Name the two phases in chromatography
- Stationary phase
- Mobile phase
Identify the mobile phase in chromatography
The solvent
Identify the stationary phase in chromatography
The chromatography paper
Describe the relationship between the solubility of a substance and how far it moves up the paper in chromatography
The more soluble the substance, the further up the paper it moves (and vice versa)
Name the value that is used to identify substances in chromatography
Rf value
Give the equation used to calculate the Rf value of a substance
distance travelled by substance/distance travelled by solvent
Outline the difference between the appearance of a mixture and a pure substance on chromatography paper
- Mixture will produce multiple spots
- Pure substance will only produce one spot
State why mixtures of ions are difficult to detect using flame tests
Some colours can be masked by others
Write method to test for sulfate ions, including the positive result
- Add sulfate to test tube
- Add dilute hydrochloric acid
- Add barium chloride
—> White precipitate will form
Name the white precipate formed in a positive sulfate ion test
Barium sulfate
Write the word equation for the reaction of magnesium sulfate with barium chloride
magnesium sulfate + barium chloride –> barium sulfate + magnesium chloride
Name the three precipitates that can form from a positive halide ion test
- Silver chloride
- Silver bromide
- Silver iodide
Identify the 3 stages of the water purification practical
- pH test
- Crystallisation
- Distillation
Explain why a pH test is done in the water purification practical
Pure water has a pH of 7
–> pH that is not 7 shows the water contains dissolved acid/alkali
Write the method to test for dissolved solids in the water purification practical
- Weigh an empty evaporating basin using a mass balance
- Fill the basin with the water sample
- Place basin on tripod and gauze
- Heat basin with bunsen burner until water evaporates
- Wait for evaporating basin to cool
- Weigh evaporating basin again
Describe the result in the water purification practical if there are dissolved solids inside the water
The mass of the evaporating basin will increase
Write a method to purify the water through distillation in the water purification practical
- Set up tripod and gauze with bunsen burner underneath
- Place conical flask with water sample on top with bung and deliver tube attatched
- Place the delivery tube into a test tube
- Place the test tube into a beaker of ice water
- Heat water sample until it evaporates
- Wait until water collects in the test tube in the beaker
