C2. Amount of Substance

Question 1

What is the definition of relative atomic mass?

Answer 1

Avg mass of an element compared to 1/12th mass of a carbon-12 atom

Question 2

What is the definition of relative formula mass?

Answer 2

Sum relative atomic masses of all atoms in a molecule, (Avg mass of 1 molecule/ 1/12th C-12)

Question 3

What is Avogadro’s constant value?

Answer 3

6.022x10^23

Question 4

How do you calculate number of moles using particle count?

Answer 4

No of moles = (No. of particles / Avogadro’s constant)

Question 5

What’s the formula for moles in relation to mass and Mr?

Answer 5

No. moles = Mass / Mr

Question 6

What is the definition of empirical formula?

Answer 6

Formula of a compound which gives the simplest ratio of atoms of each element in the compound

Question 7

What is the molecular formula?

Answer 7

Formula of a compound which gives the no. of atoms of each element in the compound

Question 8

How do you find the mass of a single atom using Avogadro’s constant?

Answer 8

mass of 1 atom = Relative atomic mass / Avogadro’s constant

Question 9

How many Cm3 are there in a Dm3?

Answer 9

1000cm3

Question 10

How do you calculate concentration of a solution?

Answer 10

Concentration (Dm3 - c) = No. moles (n) / Volume (Dm3 - g)

Question 11

What are the properties of ideal gasses?

Answer 11

Random particles in continuous random motion, Particles are point like, 0 volume, do not react when they collide, collisions are perfectly elastic, no intermolecular forces

Question 12

Whats the ideal gas equation?

Answer 12

pV = nRT

pressure(Pa) x Volume(m3) = no. of moles of gas particles x gas constant (8.31) x Temperature (kelvin)

Question 13

How do you calculate number of moles in an ideal gas?

Answer 13

n = pV / RT
moles = (pressure x volume) / (8.31 x Temperature)

Question 14

What is the definition of stoichiometry?

Answer 14

Ratio in which reactants react and products are produced in

Question 15

What is the equation for atom economy?

Answer 15

Atom economy = (Mass of product / Total mass of reactants) x 100%

Question 16

Whats the equation for total % error for equipment?

Answer 16

Sum of all % errors

Question 17

What’s the formula for % error of equipment?

Answer 17

error amount / Mass measured x 100

Question 18

What is the definition of standard solution / Volumetric solutions?

Answer 18

Solution in which the precise concentration is unknown

Question 19

How do you create a standard solution?

Answer 19

Known mass of solute dissolved in solvent and made up to a known volume

Question 20

What is the method for creating a solution?

Answer 20

Record mass of solute; add distilled water, stir ,dissolve; decant into 250cm3 volumetric flask; rinse beaker into flask; stopper flask; homogenise

Question 21

What is the method for titration?

Answer 21

Note starting volume in burette; add solution from burette in small amounts while swirling; distilled water to decant; colour change appears; repeat till 3 concordant results

Question 22

What are spectator ions?

Answer 22

Ions that do not take part in the reaction