C3- Amount of a Substance

Question 1

Avogadro’s constant

Answer 1

6.02 x 10 ^23

Question 2

Molar mass

Answer 2

Molar mass = Mass/Mr

gmol^-1

Question 3

Molecular formula vs empirical formula

Answer 3

Molecular= number of atoms of each element in a substance
e.g. H2

Empirical= Simplest whole number ratio of atoms of each element in a compound
e.g. NaCl
–> not for molecules

Question 4

What does the dot between two compound mean in an equation

CuSO4 . 5H2O

Answer 4

Within

Question 5

Experimental formula

Assumptions

Answer 5

All water has been lost
–> reheat until the mass no longer changes

No further decomposition

Question 6

What is a standard solution

Answer 6

A solution of a known concentration

Made by dissolving an exact mass of solute in a solvent

Question 7

RTP values

Answer 7

20 c 101kPa ( 1atm)

Question 8

Molar gas volume at RTP

Answer 8

24.0 dm^3mol^-1

Question 9

Equation to find empirical formula form percentage by mass

Answer 9

Mass or % / Mr of each

Find ratio of these values

Question 10

Ideal gas equation

Answer 10

PV = nRT

Question 11

Ideal gas equation

2nd half units and conversions

Answer 11

n= mol

R= gas constant, 8.31 JmolK

T= Temperature, Kelvin (K)
–> C + 273

Question 12

Ideal gas equation

1st half units + conversions

Answer 12

Pressure Pa
–> kPa x 1000= Pa
MPa x 1 000 000 = Pa

Volume m^3
dm3/1000= m3
cm3/1 000 000 = m3

Question 13

Tonnes in grams

Answer 13

1 000 000

Question 14

Atom economy equation

Answer 14

Mr of desired products / Mr of total products

High atom economy means less waste is produced

Question 15

Percentage yield equation

Answer 15

Mass of product actually obtained / Maximum theoretical mass of product obtained