How Much? & Rates and Energy Flashcards
Protons and neutrons have the same…
Mass
Mass of atoms, relative masses of proton and neutrons
1
Mass number
Total number of protons and neutrons in an atom
Why do we count only protons and neutrons to calculate the mass number of an atom?
As the mass of an electron is very small so the mass of an atom is made of it’s protons and neutrons
Atoms of the same element all have the same
Atomic number
Would should always be the same amount in an atom
Protons and electrons
Isotopes
Atoms of the same element with different numbers of neutrons
Mass number?
Top number on symbol
Atomic number
Bottom number
Neutrons how can you find the amount
Mass number - atomic number = neutrons in atom
How many protons, electrons, neutrons in an atom of 19 (top) F 9 (bottom)
Protons and electrons = 9 neutrons = 10
Relative atomic masses ( A r)
What we use to weigh atoms as too small
Relative atomic mass of an element is an ..
Average value
Real stove formula mass (M r) is found by
Adding up relative atomic masses of the atoms in it’s formula
Calculate the M r of calcium chloride CaCl2
A r of Ca = 40 A r of CI = 35.5
So M r = 40 + (35.5 multiplied by 2) = 111
What is the mass of one mole of sodium hydroxide NaOH
A r of Na = 23 A r of O = 16 A r of H = 1 so 1 mole NaOH = (23+16+1)g = 40g
Percentages how do you work them out
Relative atomic masses multiplied by relative formula mass answer multiplied by 100 = percentage
What is the percentage of carbon in carbon dioxide? CO2 carbon =12 O = 16
C= 12 O=16
M r of CO2 = 12 + (2 multiplied by 16) = 44
Percentage of carbon = (12/44) multiplied by 100= 27.3%
Empirical formula
Simplest ratio of atoms or ions in a compound
Yield of a chemical process
How much you actually make
Percentage yield
Compares amount made with maximum amount that could be made
Calculating percentage yield
Percentage yield = (amount of product collected divided by maximum amount of product possible) multiplied by 100
Maximum amount of product possible calculated by
Balanced equation for the reaction
Why is it not usually possible to get 100% yield from a chemical reaction?
Because some product may be lost collected from apparatus
Why should chemical manufacture use reactions with high yields
Reduce waste reduce pollution and makes production more sustainable
Reversible reaction
Products of the reaction can react to make the original reactants
Example of reversible reaction
Ammonium chloride ammonia + hydrogen chloride
Chemical analysis is used to ..
Identify food additives
What method can be used to analyse the colours in food
Chromatography
What is the main purpose of the gas chromatography column in GC-MS analysis?
To separate a mixture
How is relative molecular mass shown in a mass spectrum
Furthest to the right
Rates and energy, rate of a reaction measures
How fast it is
Methods used to measure rate of reaction
Rate of reaction= amount of reactant used divided by time
Rate of reaction on a graph can be found
By the gradient
Particles must do what to react
Particles Must collide with a certain amount of energy before they can react
Activation energy
Minimum energy needed to react
Factors that increase the chance of collisions
Temp, concentration of solutions, pressure of gases, surface area of solids, use of catalysts will all increase the rate of reaction
Why can catalysts be used over and over again
As not used up
Why do different reactions need different catalysts
Catalysts often work with only one type of reaction
Exothermic reactions
Reactions that transfer energy to the surroundings
Exothermic reaction examples
Combustion buring of fuels, oxidation respiration
Endothermic reactions
ReCtions that take in energy from surroundings
What are the two ways that show that a reaction is endothermic
Decrease in temp and some need supply of energy
Ectothermic changes can be used in
Hand earners based on recrystallisation
Endothermic changes can be used in
Instant cold packs
