Chemistry in Society

Question 1

activated complex

Answer 1

is a very unstable arrangement of atoms formed at the maximum of the potential energy barrier, during a chemical reaction

Question 2

activation energy

Answer 2

the minimum kinetic energy required by colliding particles before reaction will occur, since a high energy activated complex must be formed

Question 3

actual yield

Answer 3

the quantity of desired product formed in a reaction under the prevailing reaction conditions

Question 4

atom economy

Answer 4

measures the proportion of the total mass of all starting materials converted into the desired product in the balanced equation

Question 5

catalyst

Answer 5

increases the rate of a chemical reaction by providing an alternative pathway with a lower activation energy

Question 6

collision theory

Answer 6

states that, for a chemical reaction to occur, particles must collide with the correct geometry and sufficient energy to react

Question 7

endothermic reactions

Answer 7

absorb heat energy from the surroundings

Question 8

enthalpy change

Answer 8

the change in heat energy when 1 mole of reactant is converted to product(s) at constant pressure

Question 9

exothermic reactions

Answer 9

release heat energy, which is given up to the surroundings

Question 10

limiting reagent

Answer 10

determines the extent of the reaction as, being fully used up, it causes the reaction to end

Question 11

percentage yield

Answer 11

measures the degree to which the limiting reagent is converted into the desired product

Question 12

potential energy diagram

Answer 12

shows the enthalpy of reactants and products, and the enthalpy change during a chemical reaction

Question 13

temperature

Answer 13

a measure of the average kinetic energy of the particles in a substance

Question 14

theoretical yield

Answer 14

the maximum possible amount of product in a reaction i.e. if all of the reactant(s) have been converted into product.

Question 15

chromatography

Answer 15

an analytical method where mixtures are separated into their components by partitioning between a stationary and mobile phase

Question 16

dynamic equilibrium

Answer 16

achieved when the rates of two opposing processes become equal, so that no net change results

Question 17

end-point

Answer 17

the point at which the reaction is just complete

Question 18

enthalpy of combustion

Answer 18

is the enthalpy change that occurs when 1 mole of a substance is burned completely in oxygen

Question 19

equilibrium

Answer 19

the state reached by a reaction mixture when the rates of forward and reverse reactions have become equal

Question 20

hess’s law

Answer 20

the enthalpy change for a chemical reaction is independent of the route taken, providing the starting point and finishing point is the same for both routes

Question 21

mean molar enthalpy

Answer 21

the average energy required to break one mole of bonds, for a bond that occurs in a number of compounds

Question 22

molar bond enthalpy

Answer 22

the energy required to break one mole of bonds in a diatomic molecule

Question 23

molar volume

Answer 23

the volume occupied by one mole of a substance

Question 24

retention time

Answer 24

the time taken for an individual peak to traverse the gas-liquid chromatographic column after the injection time

Question 25

specific heat capacity

Answer 25

the quantity of heat required to raise the temperature of 1g of a substance by 1 degree celsius

Question 26

standard solution

Answer 26

a solution of accurately known concentration

Question 27

thermochemical equation

Answer 27

states the enthalpy change for the reaction defined, with reactants and products in the states shown

Question 28

titration

Answer 28

determines the volume of reactant solution required to react completely with the test solution

Question 29

volumetric analysis

Answer 29

involves analysis using a solution of accurately known concentration in a quantitative reaction to determine the concentration of another substance