Kinetics+Amount Of A Substance 3.1.2/5 Flashcards
Define element, Compound, Mixture
Element is a substance made from one type of atom
Compound is two or more different typed of atoms chemically combined
Mixture is two or more different types of atoms not chemically combined
Define relative atomic mass
Average mass of all the isotopes of an element relative to a 1/12 the mass of one atom of Carbon 12
Define relative formula mass
Average mass of a molecule of a molecular compound relative to 1/12 the mass of one atom of Carbon 12
Whats the unit for relative atomic mass and relative formula mass
g mol‐¹ (grams per mole)
Whyis relative atomic and formula mass compared to Carbon 12
It is the most stable and abundant isotope
Atoms are really tiny and have really small masses so using g/kg would be really difficult in calculations, therefore C-12 is the standard to compare other elements to
How do you calculate Mr (relative formula mass)
Work out the mass of each element and multiply by how many of each element there is and add all the masses together
What is the formula for calculating relative atomic mass
(Mass×abundance)+(Mass×abundance)/total abundance
Equation for Mole involving Mass and Mr
Moles=Mass/Mr
Formula to work out number of particles
Moles × Avagadros constant
Equation to calculate moles using concentration and volume
What is the unit for concentration
Moles = concentration × volume
mol dm-³
What is the formula for density and what is the unit
Density = Mass/Volume
g cm-³
What is the formula for molar volume of gas
What number is molar volume
Moles = gas volume/molar volume
24dm³/24000cm³
What are these unit conversions
Kg -> g
g -> mg
cm³ -> dm³
Tonne -> g
Tonne -> kg
Kg -> g ×1000
g -> mg ×1000
cm³ -> dm³ ÷1000
Tonne -> g ×10⁶
Tonne -> kg ×10³
What is the ideal gas equation and give the units
pV = nRT
p Pressure Pascals
V Volume m³
n Moles
R Gas Constant 8.31
T Temperature Kelvin
What is the value of the gas constant
8.31
How to convert degrees Celsius to kelvin
Why is kelvin used rather than degrees Celsius
At 0 kelvin there is…
+273
It is an absolute scale and it is more accurate than using degrees Celsius
No movement of particles
Volume conversions
1m³ -> 1000dm³ -> 1000000cm³
Pressure conversions
Kpa to Pa
mPa to Pa
KPa - 1000Pa
mPa - 1000000Pa
SAMSUNG AMOUNT OF SUBSTANCE
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Define atom economy and give the equation
When is the atom economy 100%
A measure of how efficiently atoms in the reaction are used in a chemical reaction
Mr of desired product / sum of Mr of all reactants × 100
If only one product is made as all the reactants are in the desired products
What are the economival and environmental advantages of using chemical reactions with high atom economy
ECONOMIC : Less waste products produced, less spending on sperating desired products, less spending on disposing by product
ENVIRONMENTAL : Less byproducts (pollutants) do less harmful for environment, more sustainable
What is the formula for percentage yield
Why is percentage yield never 100%
Why is percentage yield sometimes over 100%
Actually yield / Theoretical yield ×100
-Unexpected reactions occur to form unwanted products
-Reversible reactions
-Products lost during separation(filtration, distillation, crystallisation)
-Not all reactants have reacted(incomplete reactions)
-Any impurities enter the reaction system and form byproducts
Define empirical formula and molecular formula
When calculating empirical formula, when can you round up and down
EMPIRICAL FORMULA: The simple whole number ratio of the atoms of each element in a compound
MOLECULAR FORMULA: The actual number of atoms of each element in a compound
When calculating empirical formula, only round up if .85 and down if .15
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Explain how to go from empirical formula to molecular formula
- Find the empirical mass
- Divide the relative molecular mass by the empirical mass to find the factor
- Multiply each atom in the empirical formula by the factor
What does a hydrated salt contain
Water of crystallisation
Ionic equations Samsung notes
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Ionic equations Samsung notes
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Explain the titration practical
-Fill in the burette with known concentration of acid or alkali
-Record the burette reading to 2 decimal places
-Fill the pipette to a known volume of acid or alkali and transfer it to a conical flask
-Add a few drops of indicator to the flask
-Open the tap and slowly add acid or alkali from burette to the acid or alkali in conical flask and continuously Swirl the conical flask
-When a colour change is observed, end point is reached
-Record the final burette reading to 2 decimal places
-Repeat this process until you have 2 titre readings that are concorant(within 0.10cm³ of eachother)
-Calculate the average of concordant results (do not include rough titration)
Explain the colour changes for acid, neutral and alkali for the indicators, methyl orange and phenolpthalien
Phenolpthalein: Acid-Colourless Neutral-Colourless Alkali-Pink
Methyl orange: Acid-Red Neutral-Orange Alkali-Yellow
TITRATION
Formula for dilution factor
What is really important here
New volume ÷ Old volume
Volume must be in the same unit
If a titration question includes the phrase:’Placing …. cm³ into a ….cm³ volumetric flask and making up to the mark’, how would you answer this question
Work out the answer and multiplying by the dilution factor
What is the formula for percentage uncertainty
When calculating percentage uncertainty in the equipment, you have to multiple the answer by the number of times the equipment has been used, unless it says …
Uncertainty in equipment/ reading ×100
Total uncertainty of equipment
What are 2 rules for collision theory
-Particles must have sufficient energy to collide with each other and react
-Particles must collide in the correct orientation
Give 5 factors that increase the frequency of successful collisions
-Add a catalyst
-Increase surface area
-Increase temperature
-Increase pressure
-Increase concentration in a given volume
For a reaction to occur, particles must have…
Energy equal to or greater than activation energy for a reaction to occur
Explain the energy profile for an exothermic reaction
Energy of the reactants is higher than the energy of the products
Negative energy chnage as energy is released from the reaction to the surroundings
Explain the energy profile for an endothermic reaction
Energy of the reactants is lower than energy of the products
Positive energy change as energy is transferred from surroundings to the reaction
Explain the energy profile for an endothermic reaction
Energy of the reactants is lower than energy of the products
Positive energy change as energy is transferred from surroundings to the reaction
What is the curved part of an energy profile called
Transition state
What does the Maxwell Boltzman distribution show
The distribution of energy for gas molecules at a given temperature
Maxwell Samsung notes
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Even if a few particles hvae energy that is greater than or equal to the activation energy, the reaction can still reach completion as…
Particles can gain energy through collisions
What factors affect rate of reaction
Concentration
Pressure
Temperature
Surface area
Catalyst
How do Catalysts increase rates of reaction
Provide an alternative reaction pathway with a lower activation energy so more particles have an energy that is greater than or equal to the activation energy
What is beneficial about using Catalysts to speed up rate of reaction
Cheaper to speed up rate of reaction compared to using high temperatures or high pressures and Catalysts don’t get used up
How do Catalysts affect the shape of a Maxwell Boltzmann distribution
They do not have any affect(It doesn’t change the energy of molecules)
How does increasing temperature, speed up rate of reaction
When temperature increases, the kinetic energy of molecules increases so more particles have an energy that is equal to or greater than the activation energy
Does increasing temperature change the shape of the Maxwell Boltzmann distribution
Yes, a higher number of molecules have energy that is equal to or greater than the activation energy
What is on the x axis and y axis on a Maxwell Boltzmann distribution
X axis: Energy
Y axis: Number of molecules
What is another name for average energy on a Maxwell Boltzmann distribution
Mean energy
How does increasing pressure and concentration affect rate of reaction? Explain it.(Same explanation for both)
At high pressure/concentrations, there are more molecules in the same volume so the molecules are closer together so there are more frequent successful collisions, increases rate of reaction
How does increasing surface area affect rate of reaction?
Increasing surface area so more particles are exposed to other reactants so there are more frequent successful collisions
How can you increase the surface area of particles
Cutting into small pieces
Crush into a powder
Add holes/ridges
Explain the changes to a graph when you increase concentration
-The most probable energy and mean energy stays the same
-The curves will be higher and the area under the curve will be greater because there are more particles
-More moelcules have energy that is equal to or greater than the activation energy
Explain the changes to a graph when you increase temperature
-At high temperatures, the curve shifts to the right and the peak is lower
-The most probable energy shifts to the right so more particles have very high energy
-For both curves, the total area under the curve stays the same as the total number of particles stays the same
Explain the rare of reaction from the start to the end of a reaction
At the start, the reaction is fast as there are lots of frequent, successful collisions. As the concentration of reactant particles decreases, the reaction slows down. Once the reactants particles have been used up, the reaction is complete
Define rate of reaction and give its units
Change in the concentration of a substance in a given time
Unit: mol dm-3s-1
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