C6 Chemical Calculations With Mass

Question 1

Equation for concentration with mass

Answer 1

Concentration (g/dm^3) = Mass (g) / Volume (dm^3)

Question 2

What is Avogadro’s constant

Answer 2

6.02 x 10^23 (A number that represents the number of atoms, ions or molecules in one mole of a substance)

Question 3

Equation for mass and moles

Answer 3

Moles = Mass (g) / Mr

Question 4

Reactants in this equation are placed on scales, explain why the mass measurement decreases

2Na (s) + 2H2O (l) ——-> 2NaOH (aq) + H2 (g)

Answer 4

Hydrogen gas is released as a gas so won’t be weighed/measured

Question 5

Define excess reactant and limiting reactant

Answer 5

Excess reactant - The reactant that is not fully used up once the reaction is complete

Limiting reactant - The reactant is fully used up once the reaction is complete, this means it stops the reaction once it is used up.

Question 6

Convert cm cubed to dm cubed

Answer 6

Divide by 1000

Question 7

If the amount of solute in a solution is increased what happens to the solutions concentration

Answer 7

Increase in concentration

Question 8

If the volume of solvent in a solution is increased what happens to the solutions concentration

Answer 8

Decrease in concentration

Question 9

Units for concentration

Answer 9

g/dm^3 OR mol/dm^3