Amount Of Substances

Question 1

What is a mole

Answer 1

An amount of a substance. It is represented by the number
6.02 x 10^23

Question 2

What is avogradros constant and what is it used for

Answer 2

Avogardros constant is the number 6.02 x 10^23. U can use it to convert between numbers of particles (atoms) and number of moles

Question 3

What is the formula for working out number of atoms

Answer 3

Number of atoms = number of moles x avogadros constant

Question 4

How do you figure out the mass of 1 molw of any substance

Answer 4

1 mole of any substance has a mass that is Tye same as its relative molecular mass (Mr) in grams

Question 5

What is the equation for number of moles of a substance, mass of the substance and the Mr

Answer 5

Number of moles = mass of substance ÷ Mr

Question 6

Define the concentration of a solution

Answer 6

How many moles are dissolved per 1 dm³

Question 7

What is the equation for number of moles, concentration and volume

Answer 7

Number of moles = concentration x volume (dm³)

Question 8

What is the ideal gass equation?

Answer 8

PV = nRT
P = pressure in Pa
V = volume in m³
n = number of moles
R = 8.31
T = temp in k

Question 9

What are ionic equations used for

Answer 9

Can be written for any reaction involving ions that happens in a solution

Question 10

How do you write an ionic equation

Answer 10

Start by writing a full balanced reaction for the equation. Then split any dissolved ionic species into ions. Then take out any ions that appear on both sides of the equation

Question 11

How can you work out how much product you will get from a certain mass of reactant

Answer 11

You can use the balanced equation for this.
. Write out the balanced equation for the reaction
. Work out how many moles of the reactant you have
. Use the molar ratio from the balanced equation to work out the number of moles of product that will be formed from this much reactant
. Calculate the mass of that many moles of the product

Question 12

What are state symbols

Answer 12

These are symbols put after each compound in an equation. They tell you which state of matter things are in
. S = solid
. L = liquid
. G = gass
. Aq = aqueous

Question 13

What is a neutralisation reaction

Answer 13

When an acid reacts with an alkali to make salt and water

Question 14

How does titrations involve neutralisation reactions

Answer 14

Uses neutralisation reactions to work out the concentration of an acidic or alkaline solution

Question 15

What is a standard solution

Answer 15

It is any solution that you know the exact concentration of

Question 16

What does making a standard solution involve

Answer 16

Dissolving a known amount of solid into a known amount of water to create a known concentration

Question 17

How do u make a standardised solution

Answer 17

. Calculate the quantity of the substance we want to make the solution out of by using equation
Moles = concentration × volume
. Dissolved the solid into distilled water
. Transfer standard solution into volumetric flask that has been rinsed with distilled water
. Add distilled water into the volumetric flask until it reaches 1cm below the graduation mark on the flask
. Homogenise the solution

Question 18

What are the main 2 indicators used in titrations?

Answer 18

. Methyl orange
. Phenolphthalein

Question 19

How do you find the voluke of acid or alkaline that you need to neutralise a solution

Answer 19

Using the formula
Volume (cm³) = (number of moles x 1000) ÷ concentration

Question 20

What is empirical formula

Answer 20

A formula that gives the smallest whole number ratio of atoms of each element present in a compound
Eg: butane - C2H5. This means ratio of carbon to hydrogen is 2:5

Question 21

What is molecular formula

Answer 21

A formula that gives the actual number of atoms in a molecule. The molecular formula is made up of a whole number of empirical units.
Eg: butane - C4H10

Question 22

How to calculate molecular formula from empirical formula and relative formula mass

Answer 22

. Find empirical mass, which is the relative mass of the empirical formula
. Relative molecular mass ÷ empirical mass. This tells you how many multiples of empirical formula is in molecular formula
. Multiply empirical formula by that number

Question 23

How do you calculate the empirical formula from the percentages of different elements

Question 24

What is a theoretical yield

Answer 24

The mass of product that should be formed in a chemical reaction. It assumes no chemicals are lost in the process.

Question 25

How do you calculate theoretical yield of a reaction

Answer 25

By using the masses or reactants and balanced equation . Work out how many moles of each reactant you have . Use the equation to work out how many moles of product you would expect that reactant to make . Calculate the mass of that many moles of product

Question 26

How do you calculate percentage yield

Answer 26

Percentage yield = (actual yield/theoretical yield) x 100

Question 27

Why is the actual yield always smaller than the theoretical yield

Answer 27

Sometimes, not all reactants react fully, and chemicals can be lost during a reaction.

Question 28

What is atom economy

Answer 28

A measure that tells us how much of the reactants in a reaction becomes useful products rather than waste products

Question 29

What are the economical advantages of having a high atom economy

Answer 29

. Makes more efficient use of raw materials . Better as a low atom company leads to waste of money since a high proportion of chemicals used becomes wasteful useless products . Companies will have less waste to deal with

Question 30

What are the ethical and environmental advantages of atom economy

Answer 30

. Uses fewer raw materials and produces less waste so more environmentally friendly as less harmful chemicals are produced that can harm the environment . It is more sustainable . Good for society as chemical companies can find easier and cheaper ways to produce medicines, so products can be sold for lower prices and be more available to people

Question 31

How do you calculate atom economy

Answer 31

(Molecular mass of products/sum of molecular mass of all reactants) × 100