3. Quantitative chemistry (moles, limiting reactant, concentration of solutions)

Question 1

What does the law of the conservation of mass state?

Answer 1

No atoms are made or lost during a chemical reaction
mass of reactants = mass of products

Question 2

If a reaction seems to involve a change in mass, what should you check for?

Answer 2

a reactant or a product as a gas and if its mass has not been taken into account

Question 3

If the mass of reactants = mass of products, then how can chemical reactions be represented?

Answer 3

As balanced symbol equations

Question 4

Why might a gas’ mass not be taken into consideration?

Answer 4

because the gas has been released into the atmosphere

Question 5

What are chemical amounts measured in?

Answer 5

moles

Question 6

What are the units for moles?

Answer 6

mol

Question 7

What is the mass of 1 mole of a substance equal to?

Answer 7

it’s relative atomic mass

Question 8

What does 1 mole of a substance and 1 mole of any other substance contain?

Answer 8

the same number of the stated particles, atoms, molecules or ions

Question 9

What is Avogadro’s constant?

Answer 9

The number of atoms, molecules or ions in a mole of a given substance

Question 10

What is the value of Avogadro’s constant?

Answer 10

Question 11

What is the equation for number of moles?

Answer 11

Moles = Mass / Mr

Question 12

What do the big numbers in front of chemical formulas tell you?

Answer 12

How many moles of each substance there is

Question 13

What can masses of reactants and products be calculated from?

Answer 13

balanced symbol equations

Question 14

What must be the same on both sides of the equation?

Answer 14

the total moles of 1 element

Question 15

What is the limiting reactant?

Answer 15

the reactant that is used up/not in excess

Question 16

Why is the limiting reactant called the limiting reactant?

Answer 16

Since it limits the amount of products

Question 17

When does a reaction stop?

Answer 17

When all of one of the reactants is used up

Question 18

How can you find out the mass of a product formed in a reaction with the limiting reactant?

Answer 18

The mass of the limiting reactant is equal to the mass of the product formed

Question 19

In a chemical reaction involving two reactants, what will often happen?

Answer 19

you will often use one in excess to ensure that all of the other reactant is used

Question 20

What can the concentration of a solution be measured in?

Answer 20

g/dm3

Question 21

How do you calculate the mass of a solute in a given volume of a known concentration?

Answer 21

mass = conc x volume

Question 22

What gives a higher concentration?

Answer 22

a smaller volume or larger mass of solute

Question 23

What gives a lower concentration?

Answer 23

a larger volume or smaller mass of solute

Question 24

What is the equation for concentration?

Answer 24

Question 25

What is the equation for concentration involving moles?

Answer 25