Calculations involving the mole

Question 1

what ion does silver (Ag) form?

Answer 1

Ag+

Question 2

what ion does zinc form (Zn)?

Answer 2

Zn2+

Question 3

what are isotopes?

Answer 3

atoms of the same element with different number of masses and neutrons but same proton number

Question 4

what is the empirical formula?

Answer 4

the simplest whole number ratio of atoms of each element in a compound.

Question 5

what is avagodros constant?

Answer 5

the number of particles of a substance in one mole of that substance. This has a value of 6.02 times 10 to the power of 23.

Question 6

how do you calculate the amount of a substance (mol)?give units

Answer 6

mass(g)/ molar mass (g/mol) Mr

Question 7

how do you calculate the number of atoms in a substance?

Answer 7

amount of substance(mol) times the Avogadro constant.

Question 8

how do you convert from dm cubed to cm cubed?

Answer 8

times by 1000

Question 9

what is the molecular formula?

Answer 9

the number of atoms of each element in a molecule

Question 10

what is relative molecular mass?

Answer 10

the mass of a molecule compared with the mass of an atom of carbon-12.

Question 11

how do you calculate concentration (mol/dm cubed)?give units

Answer 11

amount of a substance(mol)/volume(dm cubed)

Question 12

what is the molar volume of any gas approximately?

Answer 12

24dm cubed

Question 13

how do you calculate the amount of substance (mol) of a gas at room temperature and pressure?

Answer 13

volume (dm cubed)/24

Question 14

what is the ideal gas equation?give units

Answer 14

pressure (Pa) multiplied by volume (m cubed) equals amount of substance(mol) multiplied by ideal gas constant multiplied by temperature (K)

Question 15

how do you convert from cm cubed to m cubed?

Answer 15

divide by 1 million

Question 16

how do you convert from degrees celsius to kelvin (K)?

Answer 16

add 273

Question 17

for an ideal gas, what assumptions are made?

Answer 17

-the gas molecules are tiny compared to the space between them.
-no forces acting between the gas molecules
- gas molecules move randomly
the Collins are elastic

Question 18

when is the ideal gas equation used?

Answer 18

when the gases may not be at room temperature or pressure

Question 19

how can you determine the volume from a liquid chemical?

Answer 19

1) measure the mass of an empty syringe and cap using a balance
2) remove the cap and draw a small volume of our chemical into the syringe. Replace the cap to seal the chemical.
3) reweigh the gas syringe containing the chemical and cap.
4) calculate the mass of the chemical by subtracting the initial by the other mass
5) boil the chemical so it turns from a liquid to a gas. Place the syringe in a beaker of boiling water
6) once boiled, read the volume of the gas on the scale of the gas syringe. You can use the volume to determine the molar mass of the chemical.

Question 20

what is water of crystallisation?

Answer 20

crystals which contain water molecules apart of their crystalline structure which is called a hydrated compound. In a formula, it is shown by a dot.

Question 21

in a formula, how can you tell how many water molecules are needed for a compound?

Answer 21

after the compound, a dot and the number of water molecules needed for that compound is shown.

Question 22

what occurs when you heat hydrated compounds?

Answer 22

the bonds holding the water molecules in the crystal will be broken, creating steam. An anhydrous compound is left. Anhydrous means no water in the compound.

Question 23

what does hydrated copper sulphate form?

Answer 23

blue crystals

Question 24

what are the assumptions made from the experimental formula of hydrated copper(II) sulphate?

Answer 24

assumption 1- all water has been lost

assumption 2-no further decomposition. Many salts decompose further when heated.

Question 25

how do you convert dm cubed to litres?

Answer 25

1dm cubed=1000cm cubed=1000ml=1 litre

Question 26

what is the equation that links amount of a substance(mol), concentration and volume?

Answer 26

amount (mol)=concentration (mol dm cubed) times volume (dm cubed)

Question 27

what is the equation to calculate atom economy percentage?

Answer 27

(molar mass of desired product) divided by (sum of all molar masses of all reactant) all multiplied by 100

Question 28

how do you calculate percentage yield?

Answer 28

(yield) divided by (maximum theoretical yield) all multiplied by 100. yield and maximum yield can be in grams or mols but they have to be the same

Question 29

what is relative atomic mass?

Answer 29

weighted mean mass of an atom compared with 1/12 th of carbon-12