How Much?
- Created by: DeanJowl
- Created on: 06-11-12 20:18
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- How Much?
- The mass of atoms
- The relative mass of protons and neutrons is 1.
- The atomic number of an atom is its number of protons.
- The mass number of an atom is the total number of protons and neutrons in the necleus.
- Isotopes are atoms of the same element with different numbers of neutrons.
- Masses of atoms and Moles
- We compare the masses of atoms by measuring them relative to atoms of Carbon-12
- We worl out the relative formula mass of a compound by adding up the relative atomic masses of the elements in it, in the ratio shown by its formula.
- One mole of any substance is its relative formula mass, in grams.
- Percentages and formulae
- The relative atomic masses of the elements in a compound and its formula can be used to work out its percentage composition.
- We can calculate empirical formulae given the masses or percentage composition of elements present.
- Equations and calculations.
- Balanced symbol equations tell us the number of moles of substance involved in a chemical reaction.
- We can use balanced symbol equations to calculate the masses of reactants and products in a chemical reaction.
- The yield of a chemical reaction.
- The yield of a chemical reaction describes how much product is made.
- The percentage yield of a chemical reaction tells us how much product is made compared with the maximum (100%).
- Factors affecting the yield of a chemical reaction include product being left behind in the apparatus and difficulty separating the products from the reaction mixture.
- It's important to get the highest yield and minimise energy wasted to benefit the environment.
- Reversible reactions
- In a reversible reaction the products of the reaction can react to make the original reactants.
- The reaction can be shown to be reversible by using a
- Analysing substances
- Although simpler to use than bench chemistry methods, instrumental methods still need trained technicians to operate.
- Additives may be added to food in order to improve its appearance , taste and its 'shelf life'.
- Food scientists can anaylse foods to identify additives.
- Modern instrumental techniques provide fast, accurate and sensitive ways of analysing chemical substances.
- Instrumental analysis.
- Compounds in a mixture can be seperated using gas chromatography.
- Once separated , compounds can be identified using a mass spectrometer.
- The mass spectrometer can be used to find the relative molecular mass of a compound from its molecular ion peak.
- The mass of atoms
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