C4 Chemical Calculations

Question 1

Equation which links moles, relative formula mass, and mass

Answer 1

Number of moles = mass (g)/relative formula mass

mass (g) = number of moles X relative formula mass

Question 2

% by mass equation

Answer 2

mass percent = (relative atomic mass of element/relative formula mass of compound) X 100

Question 3

Atom economy equation

Answer 3

Atom economy = relative formula mass of desired products (from equation)/ sum of relative formula masses of all reactants (from equation) X 100

Question 4

Concentration of solution(titration)

Answer 4

Concentration of solution = volume of solution/volume of titrant

Question 5

cm ^3 to dm^3

Answer 5

cm/1000

Question 6

Equation to calculate volume of gas

Answer 6

Volume (dm^3) = number of moles X 24

Question 7

Titration process

Answer 7

1. Prepare and fill a burette with acid.
2. Record the initial volume of the acid in a suitable table.
3. Using a clean, dry pipette transfer 25.0 cm3 of alkali into a conical flask.
4. Add four drops of buicable indicator to the alkali.
5. Add acid to the alkali, swirling the conical flask to mix.
6. When the indicator starts to change colour, add the acid dropwise (still swirling) until the end-point is reached.
7. Record the final volume of acid added
8. Repeat until two concordant results are obtained.