Amount Of Substance - Physical 1

Question 1

Define Relative Molecular Mass

Answer 1

The relative molecular mass (Mr) is the average mass of a molecule relative to one twelfth of the mass of an atom of carbon-12

Question 2

Define Relative Atomic Mass

Answer 2

The relative atomic mass (Ar) is the average mass of an atom of an element relative to one twelfth of the mass of an atom of carbon-12

Question 3

Define the Avogadro constant.

Answer 3

Number of particles/atoms/ions in one mole of a substance

Question 4

Write the equation that links mass of 1 mol, mass of 1 atom and Avogadro constant

Answer 4

Mass of 1 mol = mass of 1 atom/molecule X Avogadro constant

Question 5

Define percentage yield.

Answer 5

The % of a product produced by a reaction, compared to a theoretical maximum

Question 6

What can the percentage yield of a practical be used to investigate?

Answer 6

Efficiency of practical techniques and whether reactions proceed as estimated

Question 6

How would you calculate percentage yield?

Answer 6

actual yield / theoretical yield X 100

Question 7

Define atom economy.

Answer 7

% of amount of reactants made into a certain (useful) product

Question 8

How would you calculate atom economy?

Answer 8

Mr of atoms of useful product ÷ Mr of atoms of reactants

Question 9

What can the atom economy of a reaction be used to investigate?

Answer 9

Efficiency of using a specific reaction to produce a product

Question 10

Write the Ideal Gas Equation (in symbols and in words, with units for each thing)

Answer 10

PV = nRT
Pressure × volume = number of moles × gas constant × temperature
Pressure in Pa, volume in m3, temperature in K, R=8.31

Question 11

What are standard conditions?

Answer 11

25°C/298K 1atm/100kPa

Question 12

How do you convert between K and C temperatures?

Answer 12

°C to K + 273 K to °C - 273

Question 13

Define empirical formula

Answer 13

Simplest whole number ratio of atoms in a compound

Question 14

What is the equation that links mols, concentration and volume?

Answer 14

Moles = concentration × volume

Question 15

What is the equation that links moles, mass and Mr?

Answer 15

Moles = mass / Mr

Question 16

cm3 to m3

Answer 16

/ 1 million

Question 17

dm3 to m3

Answer 17

/ 1000

Question 18

titre = final - initial

Question 19

what should you do if water of crystallisation gives you weird numbers:

Answer 19

divide by smallest one

Question 20

g to mg

Answer 20

x 1000

Question 21

no. particles =

Answer 21

moles x avg. constant

Question 22

how do you calculate the empirical formula?

Answer 22

1) divide mass by atomic no. of element

2) divide by smallest from (1)

3) multiply if necessary

4) whole no. = answer