# Chemical calculations for mass and moles

?
• Created by: Mack765
• Created on: 12-01-21 18:29
What is the relative formula mass of a compound?
The sum of the relative atomic masses of the atoms in the numbers shown in the formula.
1 of 28
What is Avogadro's constant?
The number of atoms per mole of an element
6.02 x 10^23
2 of 28
Method of how to determine the concentration, volume or mass of a solution from a reaction.
1) Put the letters c,v and n (concentration, volume and number of moles) for each reactant and plug in the given information from the question.
2) Work out any unknowns that will help you to find the unknown that the question is asking for.
3) Once you ha
3 of 28
Method for working out the mass of a solute given the concentration and the volume of the solution.
1) Calculate the moles of the compound (mass/Mr)
2) Use the answer to work out the mass using:

Mass = moles x relative formula mass
4 of 28
What is meant by concentration (g/dm^3 definition)?
Concentration tells us the mass of a solute in a given volume of solution.
5 of 28
What is a solute?
A solute is a chemical that is dissolved in a solvent.
6 of 28
Key Facts - how mass and volume affect concentration.
If we increase the mass of solute and keep the volume the same, concentration will increase.

If we increase the volume of solution and keep the mass the same, then concentration will decrease.
7 of 28
What are the three equations for the g/dm^3 version of concentration?
Concentration (g/dm^3) = Mass (g)/Volume (dm^3)

Mass (g) = Concentration (g/dm^3) x Volume (dm^3)

Volume (dm^3) = Mass (g)/Concentration (g/dm^3)
8 of 28
What are the three equations for the mol/dm^3 version of concentration?
Concentration (mol/dm^3) = Mass (g)/Volume (dm^3)

Mass (g) = Concentration (mol/dm^3) x Volume (dm^3)

Volume = Mass (g)/Concentration (mol/dm^3)
9 of 28
'Mr' is the symbol for what?
Relative Formula Mass
10 of 28
Key Facts - Relative Formula Mass
It has no units

You don't use the big numbers when calculating relative formula mass (e.g 2H)
11 of 28
What are the equations linking moles, mass and relative atomic mass?
Moles = Mass (g)/Ar

Mass (g) = Moles x Ar

Ar = Mass/Moles
12 of 28
What are the equations linking moles, mass and relative formula mass?
Moles = Mass (g)/Mr

Mass (g) = Moles x Mr

Mr = Mass/Moles
13 of 28
What is the method used for balancing equations with moles?
1) Establish how many moles there are of each product and reactant, use information given in the question and the moles equation. Put that number in front of its reactant/product.
2) To make sure that each number is the lowest it can be, divide each numbe
14 of 28
What does the conservation of mass state - to do with chemical reactions?
That atoms cannot be created or destroyed during a chemical reaction - only rearranged into new substances.
15 of 28
Why may it appear that mass has decreased in a chemical reaction?
Because a gas has been produced and dissipated to the surroundings.
16 of 28
Why may it appear that mass has increased in a chemical reaction?
This is normally because one of the reactants is a gas.
17 of 28
What does a balanced symbol equation show?
The ratios of the reactants and products in a chemical reaction.
18 of 28
How to convert between dm^3 and cm^3 for volume.
Volume (dm^3) = Volume (cm^3)/1000

Volume (cm^3) = 1000 x Volume (dm^3)
19 of 28
How to convert between mol/dm^3 and g/dm^3 for concentration.
Concentration (g/dm^3) = Concentration (mol/dm^3) x Mr

Concentration (mol/dm^3) = Concentration (g/dm^3) x Mr
20 of 28
What is the theoretical yield of a chemical reaction?
The mass of a product that you'd expect to be produced.
21 of 28
What is the yield of a chemical reaction?
The amount of product that you actually get in a chemical reaction.
22 of 28
What is the equation for the percentage yield?
Percentage yield = (actual yield/theoretical yield) x 100
23 of 28
What does the atom economy of a reaction tell us?
The proportion of atoms that you started with that are part of useful products.
24 of 28
Why are higher atom economies more sustainable?
Because less atoms are being wasted in products that aren't useful.
25 of 28
What is the percentage atom economy equation?
Percentage atom economy = (Mr of useful products/Mr of all products) x 100
26 of 28
At room temperature (25 degrees) and pressure (1atm) one mole of any gas will occupy how much?
24 dm^3
27 of 28
What are the equations to calculate the number of moles in a gas?
Moles = Volume (dm^3)/24 dm^3

Moles = Volume (cm^3)/24000cm^3
28 of 28

## Other cards in this set

### Card 2

#### Front

What is Avogadro's constant?

#### Back

The number of atoms per mole of an element
6.02 x 10^23

### Card 3

#### Front

Method of how to determine the concentration, volume or mass of a solution from a reaction.

### Card 4

#### Front

Method for working out the mass of a solute given the concentration and the volume of the solution.

### Card 5

#### Front

What is meant by concentration (g/dm^3 definition)?

## Similar Chemistry resources:

See all Chemistry resources »See all Calculations, moles and yield resources »