Mole concept and stoiochemistry

Question 1

How to find AR given isotopes?

Answer 1

Take no on side and the percentage of that and add all of the isotopes together.

Question 2

What is the Mr of a molecular substance?

Answer 2

It is the the avg mass of 1 molecule of the covalent substance relative to 1/12 the mass of carbon-12

Question 3

How to find mr

Answer 3

Add molar masses and amt tgt

Question 4

What is the formula mass

Answer 4

It is the avg mass of 1 molecule of an ionic substance relative to 1/12 of the mass of carbon-12

Question 5

How to find percentage mass?

Answer 5

(Ar of element/ mr of compound)x100%

Question 6

What is the avogadro’s constant?

Answer 6

6.02x10^23

Question 7

Units for molar mass

Answer 7

g/mol

Question 8

No of moles

Answer 8

Mass/molar mass

Question 9

No of moles of gas

Answer 9

Vol of gas (dm3)/24.0dm3

Question 10

1dm3=?cm3

Answer 10

1000cm3 so u divide my 1000 to find dm3

Question 11

Concentration in g/dm3

Answer 11

Mass (g)/ volume of solvent(dm3)

Question 12

Concentration in mol/dm3

Answer 12

No.of moles/ vol of solvent (dm3)

Question 13

Concentration in mol/dm3

Answer 13

concentration in g/dm3/ molar mass (g/mol)

Question 14

No of moles using concentration

Answer 14

Concentration (mol/dm3)xvol(dm3)

Question 15

Number of moles avogadro

Answer 15

No of particles/6.02x10^23

Question 16

No of particles

Answer 16

No of molesx6.02x10^23

Question 17

Vol of gas (dm3)

Answer 17

No of molesx24.0

Question 18

Molar mass

Answer 18

Mass/no.of moles

Question 19

Mass

Answer 19

No.of molesxmolar mass

Question 20

Mass in g/dm3

Answer 20

Concentration(g/mol)/volume (dm3)

Question 21

Volume dm3

Answer 21

Mass(g)/concentration (g/dm3)

Question 22

Vol dm3 (mol)

Answer 22

No of moles (mol)/ concentration(mol/dm3)

Question 23

How to find empirical formula

Answer 23

1. Find mass in 100g sample if percentage
2. Find no. Of moles (mass/molar mass)
3. Find ratio (divide by smalles no of moles)
4. Find simplest whole no ratio (round to neares 1 dp)

Question 24

How to find n?

Answer 24

Mr of molecular formula/ mr of empirical formula

Question 25

What is the format for answering limiting reactant qns

Answer 25

_______ mol/dm3/cm3 of ______ shld react w ________ mol/dm3/cm3 ______. However ______ mol/dm3/cm3 of _______ is present. ________ is in excess. ________ is the limiting reactant

Question 26

Mole ratio is equal to ? Ratio

Answer 26

Volume ratio

Question 27

Percentage yield

Answer 27

Actual yield (lower Val)/ theoretical yield (higher Val) x100%

Question 28

Percentage yield steps given mass of 1 reactant and final mass

Answer 28

1. Find no of moles of 1 reactant 2. Compare to ratio of final mixture and find no of moles of final mixture 3. Find theoretical mass of final mixture 4. Put in formula

Question 29

Percentage purity

Answer 29

Mass of pure substance (lower Val)/ mass of substance used in reaction (higher Val) x 100%