3. Quantitative chemistry (yield, atom economy, concentration in moles, amount of substance in relation to volume of gases) Flashcards
What is the equation for percentage yield?
Why is it not always possible to obtain the theoretical yield?
- Reaction may not go to completion because it is reversible
- Some of the product may be lost when it is separated from the reaction mixture
- Some of the reactants may react in ways different to the expected reaction
What is the yield?
the amount of product obtained
Why do industrial processes have a high percentage yeild?
To reduce waste and reduce costs
Is it possible for yields to be 100%?
No, they are always less than 100% because some product always gets lost along the way
What is atom economy?
A measure of the amount of starting materials that end up as useful products
What is the equation for the percentage mass of an element in a compound?
Ar/Mr x 1000
What is the equation for atom economy?
What does 100% atom economy mean?
That all the atoms in the reactants have been turned into useful products
What does a high atom economy mean?
That the process is ‘greener’
Why are reactions with low atom economy a problem?
- they use up resources very quickly
- The reactions aren’t very profitable: raw materials are often expensive to buy, and waste products can be expensive to remove
What can concentrations of a solution be measured in?
mol/dm3or g/dm3
What can be calculated if the volumes of two solutions that react completely are known and the concentration of one solution is known?
the concentration of the other solution can be calculated
What do equal amounts of moles of gases occupy?
the same volume under the same conditions of temperature and pressure
What is the volume of 1 mole of any gas at room temperature and pressure?
24 dm3
