C5.1 Flashcards
What is the yield of a product?
It is the mass of a particular product that is formed in a chemical reaction
What is the theoretical yield?
The maximum possible mass that could be formed in a reaction, calculated using the given mass of the reactants
What do you need to know to calculate the theoretical yield?
The mass of the limiting reactant
The relative formula masses of reactants and products
The balanced equation for the reaction
What if the formula for the theoretical yield?
mass of limiting reactant
—————————————— ✖️sum of Mr for products
Sum of Mr for limiting reactant
What is the actual yield?
The mass of product that you actually make in a chemical reaction.
What is the percentage yield?
the proportion of the theoretical yield that is actually obtained in a reaction
How do you calculate the percentage yield
Actual yield
—————————. ✖️100
Theoretical yield
Why might the percentage yield be less that 100%
The reactants may react in a different way than expected
The reaction may not go to completion as some of the reactants present do not react
You may lose some of the product when you separate it from the reaction mixture and purify it.
What is the atom economy?
It is a measure of how many atoms in the reactants form a desired product
Higher the atom economy, the greater the efficiency
How do you calculate atom economy?
Sum of Mr of the desired product
—————————————————— ✖️100
Sum of Mr of all products
What is a reaction pathway
A reaction (or series of reactions) chosen for making a particular substance
What factors are considered when choosing a reaction pathway
- Yield of the product
- atom economy of the reaction
- usefulness of by-products
- rate of reaction
- equilibrium position
What is a by-product ?
A substance formed in the reaction, in addition to the desired product
1L = ? dm3
1dm3
1ml = ? Cm3
1 Cm3
How do you convert Cm3 —> dm3
➗1000
How do you convert dm3 —> cm3
✖️1000
How do you calculate the concentration in g/dm3
Mass of solute (g) ➗volume of solution (dm3)
How do you calculate concentration in mol/dm3
Amount of solute (mol) ➗ volume of solution (dm3)
How do you convert mol/dm3 to g/dm3
Multiply the molar mass of the solute to the answer
What is a titration
A method in which a neutralisation reaction is used to determine the concentration of an acid or alkali
What is a burette
A long graduated glass tube with a tap at the bottom
What is the end point of a titration
This is when the alkali is neutralised and the indicator first changes colour.
This is because the two reactants have completely reacted together
How does a titration work (generally)
You add a known volume of alkali to a conical flask
Add a few drops of a single indicator
Add acid to the flask from a burette
How do you prepare before carrying out a titration
- use a measuring cylinder or a volumetric pipette to measure 25 Cm3 of alkali solution to he conical flask
- the burette has to be clamped vertically so that you obtain accurate readings
When you have filled the burette with acid and added a few drops of indicator to the alkali you are ready
What is the titre?
The difference between the final and initial burette reading
What is a meniscus
The curve in the surface of a liquid
What does repeatable mean
A measure of how close values are to eachother when an experiment is repeated with the same equipment
What does accurate mean
A measure of how close a result is to the true value
What is precision
A measure of how close the agreement is between the measured values
What is a measuring cylinder
A piece of apparatus used to measure different volumes of solution
What is a volumetric pipette
A piece of glassware used to measure an accurate volume of solution for a titration
How do you carry out a titration?
.
What does concordat titres mean
Results from a titration that are within 0.10 Cm3 of each other
What do the results from a titration tell you?
- the two reactants used
- the volume and concentration of one of the reactants
- the volume (but not the concentration) of one of the reactants
How do you calculate concentration in mol/dm3
Amount (mol) ➗volume (dm3)
What is the meaning of molar volume
The volume occupied by one mole of a gas
What is the value for molar volume at room temperature and pressure
24 dm3/mol
How do you calculate the volume of a substance in the gas state at room temperature and pressure
Volume (dm3) = amount (mol) ✖️ 24 dm3/mol
How do you calculate the number of moles of gas if you know the volume
Amount (mol) = volume (dm3) ➗ 24 dm3/mol
