# Quantitative Chemistry Flashcards

1
Q

A

6.02 x 10^23

2
Q

what is the formula for mass?

A

moles x RAM

3
Q

What is RFM and how do you calculate it?

A

the sum of the relative atomic mass of all atoms in a compount (relative formula mass) just add it all up (eg O2- 16 x 2 = 32)

4
Q

How do you calculate the mass of one atom of a given element?

A

divide the relative atomic (or formula, if needed) mass by Avagadro’s number

5
Q

How do you calculate the percentage mass of a given element in a compound?

A

Work out each of their mass, then the total, and do a percentage.

6
Q

how do you calculate empirical formulae, when given the mass of each element in a compound?

A

Use the mass and R.A.M to find out how many moles there are of each element, then look for the ratio- divide by the smallest, if it’s not obvious

7
Q

What is the difference between empirical and molecular formulae?

A

the empirical formula is the simplest whole number of the different atoms in a molecule. For example, C2H6 is CH3
The molecular formula is the actual number (eg C2H6)

8
Q

If given the relative formula mass and empirical formula of a compound, how do you work out the molecular formula?

A

Divide the RFM by the sum of all the empirical formula’s atoms, then mutiply the number of those atoms by the result (eg: a compound has a formula of NO2 but an RFM of 92: RFM of NO2 is 46, 92 / 46 = 2, therefore the RFM of the compound is N2O4)

9
Q

How do you calculate the amount of a compound formed when a compound is burned? (eg: CaCO3 -> CaO + CO2)

A

identify the ratio of the needed substances
calculate the number of moles
use the ratio to work out the number of moles in the other substance (eg : CaO and CaCO3 are in a 1:1 ratio; if there are 0.2 moles of CaO there are also 0.2 moles of CaCO3)
then, calculate the mass of the unknown substance

10
Q

how do you calculate percentage yield?

A

Actual Yield / Theoretical Yield * 100

11
Q

what is a stoichiometric coefficient?

A

the “balancing numbers” eg, in 2Mg + O2 -> 2MgO the stoichiometric coefficient is the 2 before Mg and MgO

12
Q

what is % atom economy?

A

mass of desired product / total mass of products * 100

13
Q

how many decimetres cubed in a litre?

A

1

14
Q

what is the formula for concentration?

A

mass / volume

15
Q

what is the unit of concentration?

A

g/dm^3

16
Q

What is a 1M solution?

A

one mole dissolved in one dm^3 of solvent