1.2 Amount of Substance

Question 1

What is the definition of the mole in chemistry?

Answer 1

The mole is the amount of substance that contains as many entities as there are atoms in 12 grams of carbon-12.

Question 2

True or False: 1 mole of any substance contains Avogadro’s number of entities.

Answer 2

True

Question 3

What is Avogadro’s number?

Answer 3

Avogadro’s number is approximately 6.022 x 10^23.

Question 4

Fill in the blank: The molar mass of an element is the mass of one mole of that element in __________.

Answer 4

grams

Question 5

What unit is used to express the amount of substance?

Answer 5

Mole (mol)

Question 6

How do you calculate the number of moles from mass?

Answer 6

Number of moles = mass (g) / molar mass (g/mol)

Question 7

What is the molar mass of water (H2O)?

Answer 7

The molar mass of water is approximately 18 g/mol.

Question 8

True or False: The empirical formula represents the actual number of atoms in a compound.

Answer 8

False

Question 9

What does the empirical formula represent?

Answer 9

The empirical formula represents the simplest whole-number ratio of atoms in a compound.

Question 10

What is the molecular formula of a compound with an empirical formula of CH2 and a molar mass of 28 g/mol?

Answer 10

C2H4

Question 11

How do you convert between moles and particles?

Answer 11

Number of particles = number of moles x Avogadro’s number.

Question 12

What is the formula for calculating concentration in mol/dm^3?

Answer 12

Concentration (mol/dm^3) = moles of solute / volume of solution (dm^3)

Question 13

What is the difference between a strong acid and a weak acid?

Answer 13

A strong acid completely dissociates in solution, while a weak acid only partially dissociates.

Question 14

Fill in the blank: The concept of stoichiometry is based on the __________ of reactants and products in a chemical reaction.

Answer 14

mole ratio

Question 15

What does the term ‘stoichiometric coefficients’ refer to?

Answer 15

Stoichiometric coefficients are the numbers in front of the compounds in a balanced chemical equation that indicate the ratio of moles.

Question 16

What is the ideal gas equation?

Answer 16

The ideal gas equation is PV = nRT.

Question 17

In the ideal gas equation, what does ‘R’ represent?

Answer 17

‘R’ represents the ideal gas constant, which is 8.314 J/(mol·K).

Question 18

True or False: The volume of one mole of an ideal gas at standard temperature and pressure (STP) is 22.4 L.

Answer 18

True

Question 19

What is the standard temperature and pressure (STP) in terms of Celsius and atm?

Answer 19

STP is 0°C and 1 atm.

Question 20

How do you calculate the mass of a gas at STP?

Answer 20

Mass = number of moles x molar mass.

Question 21

What is the definition of a limiting reagent?

Answer 21

A limiting reagent is the reactant that is completely consumed first and limits the amount of product formed.

Question 22

True or False: The excess reagent is the reactant that is completely consumed in a chemical reaction.

Answer 22

False

Question 23

What is the purpose of titration in chemistry?

Answer 23

Titration is used to determine the concentration of a solution by reacting it with a standard solution.

Question 24

What is the endpoint of a titration?

Answer 24

The endpoint is the point at which the indicator changes color, signifying that the reaction is complete.

Question 25

Fill in the blank: The __________ is the volume of titrant needed to completely react with the analyte.

Answer 25

titration volume

Question 26

What is the formula for calculating the concentration of a solution after titration?

Answer 26

C1V1 = C2V2, where C is concentration and V is volume.

Question 27

What is a dilution?

Answer 27

A dilution is the process of reducing the concentration of a solute in a solution, usually by adding more solvent.

Question 28

True or False: The total number of moles of solute remains constant during a dilution.

Answer 28

True

Question 29

What is the dilution equation?

Answer 29

C1V1 = C2V2.

Question 30

How do you find the molar mass of a compound?

Answer 30

Add together the atomic masses of all the atoms in the molecular formula.

Question 31

What is the significance of the percent composition of a compound?

Answer 31

Percent composition tells you the relative mass percentage of each element in the compound.

Question 32

What is the formula for calculating percent composition?

Answer 32

Percent composition = (mass of element in 1 mole of compound / molar mass of compound) x 100.

Question 33

Fill in the blank: The __________ is the theoretical yield of a reaction based on the limiting reagent.

Answer 33

maximum yield

Question 34

What is the difference between theoretical yield and actual yield?

Answer 34

Theoretical yield is the maximum amount of product that can be produced, while actual yield is the amount produced in a reaction.

Question 35

What is the formula for calculating percent yield?

Answer 35

Percent yield = (actual yield / theoretical yield) x 100.

Question 36

Fill in the blank: The __________ is the amount of product produced in a chemical reaction.

Answer 36

actual yield

Question 37

What does the term 'concentration' refer to in chemistry?

Answer 37

Concentration refers to the amount of solute present in a given volume of solvent or solution.

Question 38

What is a saturated solution?

Answer 38

A saturated solution is one that contains the maximum amount of solute that can dissolve at a given temperature.

Question 39

True or False: Increasing temperature generally increases the solubility of solids in liquids.

Answer 39

True

Question 40

What is the relationship between the amount of substance and volume in gases?

Answer 40

At constant temperature and pressure, the volume of a gas is directly proportional to the number of moles of gas.

Question 41

What is the significance of the gas constant 'R' in the ideal gas law?

Answer 41

The gas constant 'R' relates pressure, volume, temperature, and the number of moles of a gas.