C6 - Chemical Synthesis Flashcards
What is the formula for Nitric acid?
It is HNO3.
What is the formula for Sulphuric acid?
It is H2SO4.
What ion do acidic compounds produce when dissolved in water?
H+.
What ion do alkali compounds produce when dissolved in water?
OH-.
What is the formula for Sodium Hydroxide?
NaOH.
What is the formula for Magnesium Hydroxide?
Mg(OH)2.
What do all carbonates end in?
CO3.
What do all sulfates end in?
SO4.
What are the steps for Chemical Synthesis?
- Establish the (series of) reaction(s) needed to produce the product.
- Carry out a risk assessment.
- Calculate the quantities of reactants to use.
- Carry out the reaction under suitable conditions e.g) Temperature, concentration and use of a catalyst.
- Separate the product from the reaction mixture.
- Purify the product to ensure it’s not contaminated by other products or reactants.
- Weigh the mass and calculate the percentage yield.
- Check the yield and purity by titration.
Name 3 ways of purifying a product.
- Filtration with filter paper.
- Heating evaporates away the solvent, leaving just crystals.
- Drying the product in a desciccator.
How can you check the purity of a product?
By placing a white tile under a beaker containing acid + indicator and adding the alkali.
How do you calculate the mass of a product?
Try it for the question: How much calcium oxide can be produced from 50kg of calcium carbonate?
Note: RAMs: Ca = 40, C = 12, O = 16.
1) Write down the equation:
CaCO3 –> CaO + CO2.
2) Work out the RFM of each substance - you can ignore CO2 as it is not in the question:
40+12+(3x16) –> 40+16.
3) Convert this to a ratio and calculate how much calcium oxide can be produced:
100:56.
100kg of CaCO3 produces 56kg of CaO.
Therefore, 50kg of CaCO3 produces 56/100 * 50 = 28kg of CaO.
How do you calculate the mass of a reactant?
Try it for the question: How much aluminium oxide is needed to produce 540 tonnes of aluminium?
Note: RAMs: Al = 27, O = 16.
1) Write down the equation:
2Al2O3 –> 4Al + 3O2.
2) Work out the RFM of each substance - you can ignore O2 as it is not in the question:
2[(2*27) + (3*16)] –> 4*27.
3) Convert this to a ratio and calculate how much aluminium can be produced:
204:108.
204 tonnes of Al2O3 produces 108 tonnes of Al.
Therefore, 204/108 * 540 tonnes of reactants are needed to produce 540 tonnes of Al = 1020 tonnes of Al2O3.
Titration can be used to calculate the concentration of an acid by finding out how much alkali is needed to neutralise it. Explain how this method works.
- Fill a burette with an alkali of known concentration and take an initial reading.
- If you have been given a solid acid, accurately weigh out a sample of it and dissolve it in an accurately measured volume of distilled water.
- Use a pipette to measure the aqueous acid into a conical flask. This allows you to know the precise amount of acid used.
- Add a few drops of the indicator phenolphtalein (It should stay colourless).
- Add alkali from the burette to the acid in the flash drop by drop.
- Swirl the flask to mix it well. Near the end of the reaction, the indicator will start to turn pink. Only when it changes colour permanently, it means the acid has been neutralised.
- Record the volume of alkali added by subtracting the initial reading from the final reading.
- Repeat the experiment until you get concordant results (+-0.1cm3) to ensure accuracy.
Explain how neutralisation occurs.
- When an acid reacts with an alkali, a salt and water are always made.
- The Hydrogen ions (H+) and Hydroxide ions (OH-) join up to form Water (H+ + OH- –> H2O).
- The negative ion from the acid and the positive ion from the alkali are left in solution to form the salt (e.g: Na+ acid, Cl- alkali).
- Acid + Base –> Salt + Water.
