Quantitative Chemistry

Question 1

What is relative formula mass?

Answer 1

The sum of relative atomic masses of all atoms in the molecular formula.

Question 2

What is the equation for percentage mass of an element in a compound?

Answer 2

Ar x number of atoms in that element / Mr of the compound
X100

Question 3

How many Avogadro particles are in one mole of a substance?

Answer 3

6.02 x 10^23

Question 4

How much does one mole of carbon weigh?

Answer 4

12g

Question 5

How much does one mole of nitrogen gas weigh?

Answer 5

2 x 14 = 28g

Question 6

How much does one mole of carbon dioxide weigh?

Answer 6

12 + (2 x 16) = 44g

Question 7

What is the formula for finding the number of moles in a given mass?

Answer 7

Moles = Mass/ Mr

Question 8

Complete the sentence : In a chemical reaction, mass is always __________.

Answer 8

concerved

Question 9

What is usually involved if the mass of a chemical reaction seems to change?

Answer 9

gas - escapes if the chemical reaction is in an unsealed reaction vessel

Question 10

What does it mean if the mass of a chemical reaction increases?

Answer 10

One of the reactants is a gas that is found in air.
When the gas reacts to form a part of the product it becomes contained inside the reaction vessel- so the total mass increases.

Question 11

What does it mean if the mass of a chemical reaction decreases?

Answer 11

One of the products is a gas and all reactants are solids, liquids or aqueous. Before, they are all contained in the reaction vessel but if the vessel isn’t enclosed, gas can escape causing a decrease in mass.

Question 12

What are the four steps of balancing equations using reacting masses?

Answer 12

1. Find number of moles
2. Divide moles by the smallest number of moles in the equation
3. If any aren’t integers, multiply them all to get whole numbers
4. Write a balanced symbol equation

Question 13

What happens to a reaction when a reactant is used up?

Answer 13

It stops.

Question 14

What is the name of the reactant used up in a reaction?

Answer 14

the limiting reactant

Question 15

What does the amount of product of a reaction depend on?

Answer 15

The limiting reactant

Question 16

What is RTP?

Answer 16

Room temp and pressure

Question 17

What volume does one mole of any gas occupy at room temperature and pressure?

Answer 17

24dm^3

Question 18

What is the formula to find the volume of a known gas at RTP?

Answer 18

Volume = mass/Mr x24
OR
Volume = moles of gas x 24

Question 19

What is concentration?

Answer 19

The amount of particles within a given volume.

Question 20

What is the unit of concentration?

Answer 20

mol/dm^3

OR

g/dm^3

Question 21

What is the equation to find the concentration of a solution?

Answer 21

Concentration = mass/ volume

Question 22

How many cm^3 in 1dm^3?

Answer 22

1000cm^3

Question 23

What is the equation for atom economy?

Answer 23

atom economy = Rf of desired product/ Rf of all reactants
X100

Question 24

What does 100% atom economy mean?

Answer 24

All the atoms in the reactants have been turned into the desired product.

Question 25

What is the equation for percentage yield?

Answer 25

percentage yield = actual mass/ theoretical mass X100

Question 26

What is high atom economy better for?

Answer 26

profits and the environment

Question 27

What are yields always less than?

Answer 27

100%

Question 28

Why are yields always less than 100%?

Answer 28

1. Not all reactants react
2. Could be side reactions
3. You lose some product when you separate it from the reaction mixture