calculation Flashcards
(27 cards)
What is a mole?
Mass of a substance that contains 6.02×10²³ particles.
Give the value for Avogadro’s constant.
6.02×10²³.
Which formula is used to calculate the number of moles from mass and M?
moles = mass / Mr
Which formula is used to calculate the mass of a substance from number of moles and M?
mass = moles x Mr
What is a limiting reactant?
The reactant that is completely used up in a chemical reaction.
What is a unit for concentration?
g/dm³ or mol/dm³.
Which formula is used to calculate concentration from mass and volume?
concentration (g/dm³) = mass (g) / volume (dm³).
Which formula is used to calculate volume from concentration and mass?
volume (dm³) = mass (g) / concentration (g/dm³).
Which formula is used to calculate mass from concentration in g/dm³ and volume?
mass (g) = concentration (g/dm³) × volume (dm³).
How can you convert a volume reading in cm³ to dm³?
Divide by 1000.
If the amount of solute in a solution is increased, what happens to its concentration?
Increases.
If the volume of water in a solution is increased, what happens to its concentration?
Decreases.
What is the yield of a reaction?
Mass of product obtained from the reaction.
What is the theoretical yield of a reaction?
Maximum mass of the product that could have been produced.
Why is the actual yield always less than the theoretical yield?
• Reaction may be reversible.
• Some of the product can be lost on separation.
• Unexpected side reactions between reactants.
What is the percentage yield?
Actual yield as a proportion of theoretical yield.
How is percentage yield calculated?
percentage yield = (actual yield / theoretical yield) × 100.
What is atom economy?
Measure of how many atoms of the reactants end up as useful products.
Why is a high atom economy desirable?
Results in less waste/is more sustainable.
How is percentage atom economy calculated?
percentage atom economy = (Mₘ of useful product / Mₘ of all products) × 100.
How can concentration in mol/dm³ be calculated?
moles of solute / volume (dm³)
What is a titration?
Method used to calculate the concentration of an unknown solution.
What is the end-point?
The point at which the reaction is complete (when the indicator changes colour) and no substance is in excess.
How should solution be added from the burette close to the end point?
Drop by drop, swirling in between.
