The Chemical Industry Flashcards
Nitrogen?
Exists as a diatomic molecule, N2.
It forms a triple covalent bond to form N2.
This triple bond is very difficult to break and so nitrogen is very unreactive.
Gas at room temp and pressure.
Ammonia?
NH3.
Made by reacting N2 and H2 in the Haber process.
In NH3, there are 3 covalent bonds and then a lone pair of electrons.
The lone pair means that ammonia can form hydrogen bonds with with water - making it very soluble.
Ammonia can also form dative covalent bonds (where 2 electrons from the same atom donate both electrons to form a covalent bond) using its lone pair. This means it acts as a ligand.
The lone pair also means ammonia acts as a base. It accepts protons (H+) to form ammonium ions (NH4+).
An arrow going up to the H shows the dative/coordinate bond in form the N.
Nitrogen monoxide?
NO.
Colourless gas.
Also known as nitric oxide or nitrogen(||) oxide.
Dinitrogen monoxide?
N2O.
Colourless gas with a sweet smell.
Used as anaesthesia - laughing gas.
Also known as nitrous oxide or nitogen(|) oxide.
Nitogen dioxide?
NO2.
Brown gas with a sharp, pungent smell.
Toxic.
Also known as nitogen(|V) oxide.
Tests for ammonium compounds?
Testing for NH4+.
Add sodium hydroxide (NaOH) to a test tube,
Gently heat,
If ammonia is present, ammonia gas will be produced.
Then test the ammonia gas - turns damp red litmus paper, blue.
NH4+ + OH- —> NH3 + H2O
Test for nitrate(V) ions?
Nitrate ions are NO3-
Add sodium hydroxide (NaOH) and aluminium foil to a test tube,
Add sample,
Heat,
If nitrate ions are present, they will be reduced by the aluminium to ammonia gas.
Damp red litmus paper - blue.
3NO3- + 8Al + 5OH- + 18H2O —> 3NH3 + 8(Al(OH)4)-
Define rate of reaction?
Change in the amount/concentration of a reactant or product per unit time.
Rate = amount of reactant used/product produced / time.
Make sure the units match
How can rate be measured in experiments?
For reactions that produce a precipitate - use a conical flask with a black X paper underneath. Measure time it takes for cross to go. It’s difficult to known when the cross disappears - use the same person to reduce errors.
For reactions that produce a gas - place reaction on scale and measure the mass lost of gas. Use a fume cupboard of gas is harmful or toxic. Time it.
For reactions that produce a gas - gas syringe. Time it.
For reactions that change pH - if H+ ions are produced or used up. Use a ph meter at regular intervals and then calculate the H+ ions concentration. This is used if your measuring acids or alkalis.
For reactions that change in concentration - titrations. When we do a titration, we must slow the reaction. We do this because the reaction would continue as we’re trying to measure the concentration change at regular intervals.
For reactions with colour changes - colorimeter. Measures the absorbable of light of the sample. More concentrated, the darker the colour is and the higher the absorbance.
How to slow reaction during titration?
- Dilution with deionised water.
- Cool it down.
- Add a chemical to slow the reaction. This is called quenching.
How to find rate of reaction of propanone and iodine using colorimeter?
For reactions that change colour.
The reaction goes from brown to colourless.
I2 + CH3COCH3 —> CH3COCH2I + I- + H+
Brown + colourless —> all colourless
All aq^
We plot a calibration curve using the known concentrations of iodine along the bottom (X).
Up the side - absorbance from the colorimeter.
We take samples after each conc of iodine has reacted. Then we test for absorbance of samples from these reactions and we plot them on the graph.
We can then find out the conc of different absorbances and concentrations.
