C4 Flashcards
What are the masses of atoms relative to?
They are relative to the atoms of carbon-12
How can you find Mr?
By adding up the top number on the periodic table of the atoms in the compound up.
How to find moles?
Mass(g)/Mr
What is Avogadro’s constant?
6.02x10^23 atoms
What do balanced symbol equations tell you?
The number of moles of substances involved in a chemical reaction. They can also be used to calculate the masses of reactants and products in a chemical reaction.
Why would a reaction stop early?
This is because the limiting reactant was used up so the amounts of a product formed in a chemical reaction are determined by the limiting reactant.
What is the limiting reactant?
The reactant that is not in excess.
How to find percentage yield?
(actual mass of product produced/maximum theoretical mass of product possible)x100
What is the yield?
The mass of the product that a chemical reaction produces.
What are 5 factors affecting percentage yield?
1.The reaction may be reversible
2.Some reactants may react to give unwanted products
3.Some of the product may be lost in handling or left in the apparatus
4.The reactants may not be pure
5.Some of the desired product may be lost during its separation from the reaction mixture
Why is high atom economy desired?
It conserves the earths resources, like Walter White’s 99.1% purity of meth, it minimises pollution and it is cheaper as they do not have to get rid of the unwanted products.
How to work out atom economy?
(relative formula mass of the desired product from equation/sum of the relative formula masses of the reactants from equation)x100. Any reactions that form other products as well as the desired product will fall short of 100% atom economy.
What is a solution?
A liquid mixture
What is a solvent?
Something dissolved in a solution
How to get dm^3 from cm^3
Times the cm^3 by 1000
How to find concentration?
concentration(g/dm^3)=amount of solute(g)/volume of solution(dm^3)
How to find volume of gases?
The volume of 1 mole of any gas at room temperature and pressure is 24dm^3
How to get dm^3 from 1cm^3?
Get the value and divide it by 1000
What is a titration used for?
To measure accurately what volumes of acid and alkali react together completely. The point at which the reaction is complete is called the end point of the reaction and you can use an indicator to show it.
How do you carry out a titration in 7 steps?
1.Measure a known volume of alkali into a conical flask using a volumetric pipette. However before you need to wash the pipette with distilled water then with some of the alkali.
2.Now add a few drops of the indicator and swirl.
3.Rinse the burette with distilled water and then the acid, allowing it to pass through the tap. Read the markings at eye level and record the readings.
4.Open the tap to release small amounts of acid into the flask then swirl it to make sure they are mixed.
5.Keep repeating step 4 until it changes colour. Record the reading and work out the volume of acid needed(the titre)
6.Repeat this process three times and discard anomalous results but keep the good(concordant) results and get a mean value.
7.Use the results to calculate concentration
Safety: use eye protection as some chemicals are not nice
What is activation energy?
The minimum energy needed for a reaction to occur.
What is the indicator used in a titration?
Methyl orange, starting yellow in alkali, going reddish-orange neutral
