C4- Chemical calculations Flashcards
Avogadro’s constant
6.02x10 to the power of 23
Moles equation
Moles=mass/ Ar or Mr
What is a mole representing?
The relative formula mass in grams
Limiting reactant
The reactant that is used up first in a reaction
Percentage yield equation
actual mass of product/theoretical mass of product x 100
Yield
The mass of product that a chemical reaction produces
Reasons why percentage yield isn’t 100%
-Reaction may be reversible
-Some product may be left on apparatus
-Some product may be lost in separation from mixture
3 reasons atom economy is important?
-Conserves Earth’s resources
-Helps company make more money
-Prevent expenses to get rid of waste
Percentage atom economy equation
Relative formula mass of wanted product/ sum of relative formula masses of reactants x 100
Concentration equation and units
Amount of solute (g) / volume of solution(dm3)
1cm3 in dm
1dm3 in cm
0.001dm3
1000cm3
2 ways to increase the concentration of a solution
-Add more solute to the same volume
-Evaporate some water, lower volume, higher mass
What is titration used for?
To accurately measure what volumes of acid and alkali react completely
What is the end point of a titration?
The point at which a reaction between an acid and alkali is complete
How to carry out a titration
-Use pipette and pipette filler, measure a known volume of alkali into a conical flask
-Add a few drops of indicator, place on white tile and swirl
-Pour the acid into the burette, record volume
-Slowly allow acid into conical flask, swirl, until solution changes colour
-Calculate volume of acid in the flask, repeat until the results are concordant
