Stoichiometry and the mole pt.1

Question 1

what is Exothermic

Answer 1

releasing heat

Question 2

what is Endothermic

Answer 2

absorbing heat

Question 3

Macroscopic observation –
indications of a chemical
reaction could include:

Answer 3

a change in colour
* a change in temperature
* the evolution of heat
* a change of phase (e.g.
precipitation of a solid out of a
solution)
* the emission of light.

Answer 4

A chemical reaction is the mixing of two or more species (reactants) to
produce new substances (products).

Answer 5

• Writing balanced chemical equations describes what happens when a
  chemical reaction occurs.

Question 6

what is stoichiometry

Answer 6

• Stoichiometry is concerned with the relative amounts of reactants and
  products in a chemical reaction.

Answer 7

Stoichiometric coefficients are used to balance an equation to meet this
condition

Question 8

what does (aq) meaning

Answer 8

– (aq) meaning ‘aqueous solution’.

Question 9

Balancing chemical equations step 1:

Answer 9

– Step 1: Write the unbalanced ‘equation’.

Count the number of each element present. Is the equation balanced?

Question 10

Balancing chemical equations step 2:

Answer 10

balance the equation spastic

Question 11

Balancing chemical equations step 3:

Answer 11

adjust the stoichiometric coefficients

Question 12

what is the mole

Answer 12

• The mole (abbreviated mol) is the SI unit of amount of substance.

Question 13

what does avogadros number do

Answer 13

Avogadro’s constant (6.022 × 1023 mol–1) gives the number of entities in 1
mole.

Answer 14

The number of specified entities in a mole is constant

Answer 15

• The mass of 1 mole depends on the mass of the individual entities.

Answer 16

A sample of an element with a mass equal to that element’s average atomic mass contains one mole of atoms.

Question 17

explain M = m/n

Answer 17

• M is molar mass (in grams/mol).
• m is mass (in grams).
• n is the number of moles (in mols).

Question 18

what is the molar mass

Answer 18

• The molar mass, M, is the mass of 1 mol of a substance.

Answer 19

balanced equation gives relative number of reactant and product molecules that participate in chemical reaction

the coefficients of a balanced equation give the relative numbers of molecules

Question 20

what can a balanced equation predict

Answer 20

the moles of product that a given number of moles of reactants yield

Question 21

why is mole-to-mass conversion so crucial

Answer 21

determining reactant quantities
predicting product yield
quality control in manufacturing
environmental application

Question 22

what is mole

Answer 22

a unit used to measure the amount of a substance

Question 23

molar mass

Answer 23

mass of one mole of a substance

Question 24

what percentage yield

Answer 24

% yield = actual yield / theoretical yield x 100%

Question 25

things to note about the percentage yield calculation

Answer 25

this calculation may be done in either grams or moles - but units must be the same for both yields the actual yield can never be more than the theoretical yield

Question 26

limiting reagents

Answer 26

the limiting reagent is the reactant that is consumed first the calculated amount of a product is always based on the limiting reagent

Question 27

what is excess

Answer 27

any reagent not completely consumed during the reaction is in excess

Question 28

stoichiometric mixture

Answer 28

contains the relative amounts of reactants that matches the numbers in the balanced equation