Quantitative chemistry

Question 1

Define relative formula mass (Mr).

Answer 1

The Mr of a compound is the sum of the Ar values of all the atoms in its formula

Question 2

State the equation for the number of moles.

Answer 2

mass
moles = ———————–
Mr

Question 3

What is Avogadro’s constant?

Answer 3

Avogadro’s constant is
6.022 × 10^23. It represents the number of atoms, ions, or molecules in one mole of a substance.

Question 4

What is the formula for percentage yield?

Answer 4

percentage yield =
Actual yield
——————–
thermotical yield

Question 5

What is atom economy formular

Answer 5

atomic economy =
Mr of desired product
————————————
total Mr of reactants

Question 6

What is the formula for concentration?

Answer 6

concertation (mol/dm^3) =
moles
————————————-
volume (dm^3)

Question 7

How would you prepare 250 cm³ of 1 mol/dm³ sodium chloride solution?

Answer 7

Use the formula
Moles=Concentration x Volume.
Moles needed =
1× 0.25 = 0.25
 moles
1×0.25=0.25moles.
Mass = Moles × Mr:
0.25 × 58.5 = 14.625g