C2 3 Moles Flashcards
What is the atomic number equal to?
The atomic number is equal to the number of protons (which equals the number of electrons).
What is the relative mass of a proton, neutron and electron?
The relative masses of protons and neutrons are 1 and the electrons are 1/2000.
What is the mass number?
The mass number is the total number of protons and neutrons in its nucleus.
What are isotopes?
Isotopes are atoms of the same element with different numbers of neutrons.
Important Mole equation
Mass = Mr x moles
What is a mole?
A mole of any substance is its relative formula mass in grams.
What is the empirical formula?
The empirical formula is the smallest formula present in a compound.
Empirical formula example:
A hydrocarbon has 75 % carbon and 25 % hydrogen.
Imagine we have 100 g of the compound
So you would have 75g and 25g
As mass = Mr x moles
75/ 12 and 25/1 are the moles. Note that the 12 is the Ar of carbon and 1 is the Ar of hydrogen.
So the carbon forms 6.25 moles and the hydrogen forms 25 moles.
The ratio in its simplest form is 1:4 as you can divide 6.25 into 25.
The empirical formula is then CH4.
What does the yield of a chemical reaction show?
This shows how much product is made.
What does the percentage yield show?
The percentage yield tells us how much product is made compared with the maximum amount that could be made (100%).
What factors affect the yield of a chemical reaction?
- The reaction may be reversible.
- Some reactants may react to give unexpected products.
- Some of the product may be lost in handling or left behind in the apparatus.
- The reactants may not be completely pure.
- Some chemical reactions produce more than one product so it may be difficult to separate the product that we want from the reaction mixture.
Why is it important to maximise yield?
- To reduce pollution.
- Minimise energy consumption.
- Conserve the earth’s limited resources.
- Less waste.
