Topic 3-Quantitave Chemistry

Question 1

What is relative atomic mass?

Answer 1

The mass of all the atoms in the compound

Question 2

How do you find the percentage mass of an element in a compound?

Answer 2

Ar of the element/Ar of the whole compound

Question 3

What is a mole?

Answer 3

A mole is the name given to an amount of a substance
The Ar of the substance shows how much one mole of the substance weighs
Eg if a substance has an Ar of 12, that means that 1 mole weighs 12g

Question 4

What is the formula to find the number of moles?

Answer 4

Mass
No of Mr
moles

Question 5

What does the conservation of mass mean?

Answer 5

I’m a chemical reaction, mass is always conserved this means that no mass is created or destroyed so the mass at the beginning equals the mass at the end

Question 6

Why might the mass change?

Answer 6

If there is a gas involved. The gas can either escape, or react to form part of the product

Question 7

What is a limited reactant?

Answer 7

Reactions stop when one reactant is used up. Any other reactants are in excess.
The reactant rays used up is called the limiting reactant, because it limits the amount of product made.
The amount of product formed is directly proportional to the limiting reactant

Question 8

How much does one mole of gas occupy? and at what temperature

Answer 8

24dm cube and 20degrees

Question 9

What is the formula to find the volume of any gas?

Answer 9

Mass of the gas (g)/ Mr of the gas X24

Question 10

What is concentration?

Answer 10

Concentration is the measure of how crowded things are. The more solute (substance dissolved) there is the more concentrated the solution is

Question 11

What is the formula for concentration?

Answer 11

Mass of solute (g)
concentration Vol of solvent(dm3)
g/dm3

Question 12

What are titrations?

Answer 12

Titrations are experiments that let you find out how much volume is needed for 2 solutions to fully react

Question 13

What is the formula of concentration if you have Mol/dm3?

Answer 13

no.of moles

concentration Vol. of solvent

Question 14

How do you convert mol/dm3 to g/dm3?

Answer 14

Use the mole equation

mass (g)=moles X mr

Question 15

What is Atom economy?

Answer 15

The atom economy of a reaction tells you how much of the mass of the reactants is wasted and how much ends up as useful products

Question 16

What is the equation for atom economy?

Answer 16

Atom economy %= Mass of desired products/ mass of all the reactants

Question 17

If a reaction has 100% atom economy, what does it mean?

Answer 17

This means that all of the reactants in the reactions have been reacted into useful products.

The higher the atom economy, the greener the process

Question 18

What is a high atom economy good for?

Answer 18

A high atom economy is good for profits and the environment.
If a reaction has a low atom economy, it is producing a lot of waste which damages the environment and isn’t profitable. or it isn’t sustainable

Question 19

What is percentage yield?

Answer 19

Percentage yield shows how much product was made compared to how much was expected to be made.

Compares actual and theoretical yield

Question 20

What is the formula for percentage yield?

Answer 20

= Actual yield / theoretical yield X100

^in g

Question 21

What does 0% yield means?

Answer 21

That no product was made

Question 22

Why do industrial processes need to have high percentage yield?

Answer 22

To reduce waste and costs

Question 23

Why are yields always less than 100%?

Answer 23

Some product or reactant is always lost

Question 24

What can go wrong in industrial processes?

Answer 24

Not all of the reactants react to make a product- in reversible reactions the product can go back to being reactants

There might be side reactions- the reactants might react with gases in the air or impurities in the mixture making extra product.

Some product might be lost when you separate it from the reaction mixture