Amounts Of Substances

Question 1

5.1 Amount of Subastances: Moles

Moles (n)

Answer 1

How much a substance you have regardless its state

Question 2

5.2 Amount of Subastances: Avogadro’s Constant in calculations

1 mol/ Avogadro’s Constant

n x Avogadro’s Constant = how many atoms in compound

Answer 2

6.02 x 10 23

Question 3

5.2 Amount of Subastances: Avogadro’s Constant in calculations

1 Mole of any substance

Answer 3

Has the same weight of its Mr

Question 4

5.3 Amount of Subastances: Moles Eq

n = m/ Mr

(solid)

Answer 4

moles
(mol) = mass (g) / molecular mass
moles (mol) = mass (g) / molar mass

Question 5

5.3 Amount of Subastances: Moles Eq

n = cv

(liquid)

Answer 5

moles (mol) = concentration (mol dm-1) x volume (dm3)

Question 6

5.3 Amount of Subastances: Conversions

1dm3 = 1L

Question 7

5.3 Amount of Subastances: Conversions

1dm3 = 1000cm3

Question 8

5.4 Amount of Subastances:

Molecular Formula

(Multiple Emperical)

Answer 8

Actual number of atoms of each element in a molecule

Question 9

5.4 Amount of Subastances:

Emperical Formula

(Shortest)

Answer 9

Smallest whole number ratio of atoms of each element in a compound

Question 10

5.5 Amount of Subastances: Calculating EF

Empirical Formulae

Answer 10

1) Find Empirical mass (Mr)
2) Divide given Molecular mass by Mr
↳ works out empirical unit

Question 11

5.5 Amount of Subastances: Calculating MF

Molecular Formulae

Answer 11

Multiple Empirical Formular by Emperical unit

Question 12

5.5 Amount of Subastances:

pV = nRT

(gasses & volatile liquids)

Answer 12

p: Pressure (Pa) [1KPa = 1000Pa]
V: Volume (m3) [1cm3 = 1 x10 -6 m3]
n: number of moles (mol)
R: gass constant (8.314JK -3)
T: Temperature (K) [K = °C +273]

Question 13

5.5 Amount of Subastances: EF using composition by mass/percentage

When given a % instead of mass

Answer 13

Percentage = Mass

• If you get a whole number = ANSWER
• Otherwise divide answer in part 1 by smallest mole value

Question 14

5.6 Amount of Subastances: Write Balanced Ionic Eq

Ionic Equations

(neutralisation/titration)

Answer 14

1) Write down balanced Molecular Formula
2) Add state symbols
3) Neut reactions (acid + base), 2 products formed (salt + water)
4) Water = always (l) Rest = (aq)
5) Split (aq) solutions into respective ions, NOT WATER
6) Remove duplicates on either sides of arrow
7) What is left over = final eq.

Question 15

5.6 Amount of Subastances: Write Balanced Ionic Eq

Ionic Equations

(carbonate)

Answer 15

Similar to neut but:
1) Water = (l) CO2 = (g) Rest = (aq)
2) Don’t split up (l) & (g)
3) What is left over = final eq.

Question 16

5.6 Amount of Subastances: Write Balanced Ionic Eq

Ionic Equation

(sulfuric acid)has 2 protons→release into reaction→ produces double I eq

Answer 16

Only when Sulfuric Acid reacts w a base containing a G1 metal base, Na2SO4 is produced
↳ where the metal doubles, the 2 goes after the metal

Question 17

Percentage composition of element X

Answer 17

Total mass of element in compound / total mass of compound x 100

% comp of X = Ar/Mr x100

Question 18

n of a Gas

Answer 18

n = v/Mr
moles = volume (dm3) [given volume] / molar gas volume (dm3) [according to PT]

Question 19

At constant temp & pressure

Answer 19

1 mol of any gas occupies the same volume

Question 20

RTP

Room Temp & Pressure

Answer 20

24 mol dm3
- 293K
- 101KPa

Question 21

STP

Standard Temp & Pressure

Answer 21

22.4 mol dm3
- 293K
- 101KPa