Topic 1 - Stoichiometric Relationships

Question 1

What are the properties of matter?

Answer 1

• has a mass
• occupies a volume in space
• particles are in constant motion
• made up of particles - atoms, molecules or ions

Question 2

What is the difference between temperature and heat?

Answer 2

t - the measure of heat or kinetic energy

h - the energy of an object that raises its temperature

Question 3

What is melting?

Answer 3

the change of a state in which a solid becomes a liquid by adding heat or changing pressure

Question 4

What is boiling?

Answer 4

the conversion of liquid to vapour within the liquid as well as its surface

Question 5

What is an endothermic reaction?

Answer 5

• when greater amount of energy is required to break existing bonds in the reactants than is released when the new bonds form in products
• absorbs energy

Question 6

What is an exothermic reaction?

Answer 6

• a reaction that transfers energy from the reactants to the surroundings usually as heat
• products have less potential energy than the reactants

Question 7

What are the properties of a pure substance?

Answer 7

• definite and constant composition

- definite chemical and physical properties

Question 8

What is the difference between a homogeneous and heterogeneous mixture?

Answer 8

homo - uniform composition and properties throughout, cannot be easily separated
hetero - non-uniform composition and varying properties, components are readily distinguishable

Question 9

What is an element?

Answer 9

made up of atoms of the same atomic number

Question 10

What is a compound?

Answer 10

• made up of a combination of atoms or ions in a fixed ratio and with individual properties
• chemical bonding

Question 11

What is a mixture?

Answer 11

• combination of two or more pure substances that retain their individual properties
• physical bonding

Question 12

What is a combination/synthesis reaction?

Answer 12

combination of two or more reactants to produce a single product

Question 13

What is a decomposition reaction?

Answer 13

involve a single reactant being broken down into two or more products (AB → A + B)

Question 14

What is a single-replacement/displacement reaction?

Answer 14

a chemical change in which one element replaces a second element in a compound

Question 15

What is a double-replacement reaction?

Answer 15

• when two elements replace and exchange ions with each other in a chemical reaction
• produces a precipitate, water or a gas when two ionic compounds in a solution are combined (AB + CD → AD + CB)

Question 16

What is the ideal chemical process?

Answer 16

amount of reactants = amount of products

Question 17

What is Atom Economy?

Answer 17

• fraction of atoms of starting materials incorporated into the desired final product in a chemical reaction
• (molecular mass of desired products/molecular mass of all products) x 100

Question 18

What is the Avogadro’s constant?

Answer 18

• 6.02 x 10^23

- number of particles in one mol

Question 19

What is the molar volume of an ideal gas at STP?

Answer 19

22.7 dm^3/mol

Question 20

What is a mole?

Answer 20

a fixed amount of a substance

Question 21

What is an isotope?

Answer 21

atoms of a single element that posses different numbers of neutrons

Question 22

What is the relative abundance?

Answer 22

a measure of the percentage of each element - isotopes each have various mass numbers

Question 23

What is the relative atomic mass, Ar?

Answer 23

the weighted mean mass of an atom of an element compared with one-twelfth of an atom of carbon-12

Question 24

What is the relative molecular mass, Mr?

Answer 24

average mass of a molecule relative to the mass of a 12C atom taken as exactly 12

Question 25

What is the molar mass?

Answer 25

the mass of one mole of a substance (g/mol)

Question 26

What is the empirical formula?

Answer 26

the simplest whole number ratio of atoms or amounts of each element present in a compound

Question 27

What is concentration?

Answer 27

• the amount of substance present in a certain volume

- the amount of mass per unit volume

Question 28

What is the molecular mass?

Answer 28

• the actual number of atoms or amounts of elements in one structural unit or one mole of the compound
• multiple of the empirical formula, can be determined if the Mr is known

Question 29

What is the limiting reagent?

Answer 29

• reagent that determines the amount of product that can be formed by reaction
• reactant that is completely consumed in the reaction

Question 30

What is the theoretical yield?

Answer 30

• the amount of product that could form during a reaction calculated from a balanced chemical reaction
• represents the maximum amount of product that could be formed from a given amount of reactant

Question 31

What is the experimental yield?

Answer 31

actual amount of products produced when the reaction is carried out

Question 32

What are the 5 factors that reduce yield?

Answer 32

• loss of products from reaction vessel
• impurity of reactants
• changes in reaction conditions
• reverse reactions consuming products
• existence of side reactions due to impurities

Question 33

What is pressure and how can it be increased?

Answer 33

• force exerted by a gas as its particles collied with a surface
• increasing the frequency or energy of the particles colliding with the container walls

Question 34

What is a solution?

Answer 34

homogeneous mixture of solute dissolved in a solvent

Question 35

What is a solute?

Answer 35

the less abundance component (usually a solid)

Question 36

What is a solvent?

Answer 36

• the more abundant component (usually liquid)

- the substance in which another substance is dissolved

Question 37

What is the molar concentration?

Answer 37

the amount (in mol) of a substance dissolved in 1dm^3/1L of solvent

Question 38

What is titration?

Answer 38

• a laboratory procedure used to determine the molarity (unknown concentration) of an acid
  uses a base such as NaOH to neutralise a measured volume of an acid

Question 39

What is volumetric analysis?

Answer 39

procedure in which we measure the volume of reagent needed to react with analyse

Question 40

What is an analyte?

Answer 40

substance that is being analysed or tested by a given analytical procedure