PAPER 2 unknown things Flashcards
List two properties of alkali metals.
- Soft
- Relatively low melting point
What’s observed when Lithium reacts in water?
- Gentle bubbling
- Does not melt
What’s observed when Sodium reacts in water?
- Floats on water
- More bubbling, causing the metal to move around on the surface of the water
- The sodium melts
What’s observed when Potassium reacts in water?
- Melts into a shiny ball
- Violent bubbling
- Moves rapidly across the surface of the water
- Burns with a lilac flame
What is the colour and state of chlorine at room temperature?
Pale green gas
What is the colour and state of bromine at room temperature?
Red-brown liquid
What is the colour and state of iodine at room temperature?
Black solid
What’s the chemical test for chlorine gas?
Place damp litmus paper into a test tube of the gas. If the paper turns red then white, chlorine is present due to its bleaching effect.
What are the colours of the different halide solutions?
Chlorine - colourless
Bromine - orange
Iodine - brown
How can rate of reaction be measured when a precipitate is formed?
Place a black cross beneath the beaker. Measure the amount of time until the cross can no longer be seen. This is inaccurate however as this can be subjective.
What is the equation for anaerobic respiration in plants?
Glucose -> ethanol + CO2
What fraction of crude oil is used for surfacing roads?
Bitumen
What type of reaction is cracking?
Thermal decomposition
What is the current composition of the Earth’s atmosphere?
Nitrogen: 78%
Oxygen: 21%
Argon: 0.93%
Carbon dioxide: 0.04%
How do you test for aqueous metal ions?
Add sodium hydroxide to the solution.
What is observed when sodium hydroxide reacts with ammonium ions?
A pungent-smelling gas is produced (NH³) Which will turn damp red litmus paper blue.
How do you test for carbonate ions?
Add a few drops of HCl to the sample, then connect test tube to limewater and let the gas bubble through. If carbonate ions were present, they would have reacted to produce CO², which would have turned the limewater cloudy.
How can you test for sulphate ions?
- Add HCl to the sample to remove any carbonate ions, as these would obscure results.
- Add some barium chloride.
- If sulphate ions are present a white precipitate will form.
How do you test for halide ions?
- Add some nitric acid to remove carbonate ions.
- Add some silver nitrate.
- Observe the precipitate.
How can flame photometry be used to calculate the concentration of metal ions?
Take readings from a flame photometer of known different concentrations of metal ions, then plot a calibration curve. Then take readings of the sample and compare to the curve.
How can bromine water differentiate between alkanes and alkenes?
Bromine water will have no effect on alkanes, but when added to alkenes, will turn the solution from orange to colourless.
What are the properties of poly(propene)?
- Flexible
- Strong
- Used for buckets and crates
What are the properties of poly(ethene)?
- Inexpensive
- Electrical insulator
- Flexible
- Used for plastic bags, bottles and coating of electrical wires
What properties does poly(chloroethane) (PVC) have?
- Tough
- Cheap
- Long product life
- Used to make window frames
