Topic 1.3: Reacting masses and volumes

Question 1

Limiting reagent

Answer 1

Determines the amount of products formed.

Question 2

Excess reagent

Answer 2

Exceeds those required to react with the limiting reagent

Question 3

Theoretical yield

Answer 3

What is theoretically possible to produce when a reaction is carried out under ideal conditions.

Question 4

Factors that reduce yield of products

Answer 4

a) Impurity of reactants
b) Changes in reaction conditions (e.g. temperature and pressure)
c) Reverse reactions consuming products in equilibrium systems
d) Existence of side-reactions due to the presence of impurities

Question 5

Experimental yield

Answer 5

Actual amount produced in the process

Question 6

Percentage yield

Answer 6

% yield = (experimental yield / theoretical yield) (100)

Question 7

Kinethic theory of gases

Answer 7

Model used to explain and predict the behavior of gases at a microscopic level

Question 8

Assumptions of the KTG

Answer 8

a) Gases are made up of very small particles, separated by large distances
b) Gases particles are constantly moving in straight lines, but random directions
c) Gaseous particles undergo elastic collisions with each other and the walls of the container. No loss of kinetic energy occurs.
d) Gaseous particles exert no force of attraction on other gases

Question 9

Ideal gas

Answer 9

a) Obeys the postulates of the kinetic theory of gases
b) At high temperature and low pressure, the significance of any forces of attraction between the gas molecules is minimized.

Question 10

What happens to a gas at high pressure and low temperature?

Answer 10

The particles move more slowly and the distances between the particles decrease

Question 11

Standard temperature and pressure

Answer 11

a) 0 °C / 273 K

b) 100 kPa

Question 12

Molar volume of an ideal gas at STP

Answer 12

22.7 dm3 mol-1

Question 13

Avogadro’s law

Answer 13

Equal volumes of any gas measured at the same temperature and pressure contain the same number of molecules.

Question 14

Gas laws

Answer 14

a) Boyle’s
b) Charles’
c) Gay-lussac’s

Question 15

Boyle’s law

Answer 15

a) Temperature reamins the same.

b) As volume increases, pressure decreases.

Question 16

Charles’ law

Answer 16

a) Pressure remains the same.

b) As temperature increases, volume increases.

Question 17

Gay-lussac’s law

Answer 17

a) Volume remains the same.

b) As temperature increases, pressure increases

Question 18

Combined gas law for a fixed amount of gas

Answer 18

pV/T = pV/T

Question 19

Ideal gas equation

Answer 19

pV = nRT

Question 20

pV = nRT

Answer 20

p = Pressure (Pa)
V = Volume (m^3)
n = Amount of matter (mol)
R = Constant
T = Temperature (K)

Question 21

Ideal gas constant

Answer 21

8.31 J K^-1 mol^-1

Question 22

Solution

Answer 22

Homogeneous mixture of a solute that has been dissolved in a solvent

Question 23

Aqueous solution

Answer 23

When the solvent is water

Question 24

Molar concentration

Answer 24

Amount (in mol) of a substance dissolved in 1 dm^-3 of solvent.

Question 25

Titration

Answer 25

A standard solution of known concentration is added to a solution of unknown concentration until the chemical reaction is complete.