Unit 3 Flashcards
What are the two triangles used for calculations based on balanced equations
/\
/M\
——-
/N | gfm\
/\ / n\ ------- /c | v \
What is a limiting factor
During a chemical reaction, product is continually formed until one of the reactants is completely used up
How do you calculate the molar volume
Density= mass
Volume
What is the average molar volume of a gas At standard temperature and pressure
22.4l
Solids liquids and solutions are considered to……..when compared paired with gases
Have no volume
What does dynamic equilibrium mean for the product yield?
We do not get 100% product
What is the formula for percentage yield?
Py=Ay
Ty X100
What is theoretical yield
The expected mass produced from a known mass of reactant, which is calculated from a balanced equation
What is actual
The mass of desired product obtained which is less than the theoretical yield
The actual yield is less than the theoretical yield because…
The reaction hasn’t gone to completion i.e dynamic equilibrium
Other reactions are occurring that that compete with the desired reaction
Separation of desired products is difficult (i.e distillation)
The product maybe impure or lost during purification
Industrial processes require a high yield and high purity of products, therefore, unreacted reactants are recycling
Describe percentage yeild
Gives us information relative to the amount (%) of reactants that have successfully converted into products (During dynamic dynamic equilibrium reactions) it does not give information regarding by products formed
What can make by products costly to deal with?
If they are -Toxic -Corrosive -Flammable I.e by products harmful to the environment
What makes a reaction most desirable (in an Atom Economy sense)
Reactions in which most of the reactant atoms are converted into products
What is the formula for Atom Economy?
Total mass
of desired product
Atom Economy= __________
Total mass of
All reactants
A reversible reaction is…
One that proceeds in both the forward and reverse direction
Reversible reactions reach a state of dynamic equilibrium when…
the rate of the forward reaction is exactly equal to the rate of the reverse reaction
At dynamic equilibrium there is NOT 50% reactants and 50% products however….
The concentrations of the reactants and products was constant at dynamic equilibrium
Name the three ways the dynamic equilibrium can be changed
Concentration
Pressure
Temperature
What is the Le chatelier’s principle
If a system at equilibrium is subject to any change, the system readjusts itself to counteract the applied change
Consider the following reaction
A+B 🔁C+D
What would happen if you increased the concentration of A or B
According to le chateliers principle
The system will decrease the concentration of A or B
By promoting the forward reaction
Moving the equilibrium to the right producing more product (ie C+D)
Consider the following reaction
A+B 🔁C+D
What would happen if you decreased the concentration of C or D
According to le chateliers principle
The system will increase the concentration of C or D
By promoting the forward reaction
Moving the equilibrium to the right producing more product (ie C+D)
Consider the following reaction
A+B 🔁C+D
What would happen if you decreased the concentration of A or B
According to le chateliers principle
The system will increase the concentration of A or B
By promoting the reverse reaction
Moving the equilibrium to the left producing more reactants(ie C+D)
Consider the following reaction
A+B 🔁C+D
What would happen if you increased the concentration of C or D
According to le chateliers principle
The system will decrease the concentration of C or D
By promoting the reverse reaction
Moving the equilibrium to the left producing more reactants (ie A+B)
The effects of changing pressure on a system involving gasses is equivalent to ….
The effects of changing concentration
Consider the following reaction
3A(g)+B(g) 🔁2C(g)
What would be the effect of increased pressure?
According to le chateliers principle
The system will decrease the pressure
By promoting the forward reaction
Moving the equilibrium to the right producing more products
Consider the following reaction
3A(g)+B(g) 🔁2C(g)
What would be the effect of decreased pressure?
According to le chateliers principle
The system will increase the pressure
By promoting the reverse reaction
Moving the equilibrium to the left producing less products
Pressure has no effect when both the reactants and products….
Occupy the same volume
Consider the following reaction
3A(g)+B(g) 🔁2C(g)
↗️ ↖️ Exothermic Endothermic
What would be the effect of decreased temperature ?
According to le chateliers principle
The system will increase the temperature
By promoting the forward reaction
Moving the equilibrium to the right producing more products
Consider the following reaction
3A(g)+B(g) 🔁2C(g)
↗️ ↖️ Exothermic Endothermic
What would be the effect of increased temperature ?
According to le chateliers principle
The system will increase the temperature
By promoting the reverse reaction
Moving the equilibrium to the left producing less products
A catalyst does not…
change the equilibrium position
A catalyst…
Speeds up the rate of reaction of a chemical reaction by providing an alternative reaction pathway with a lower activation energy
In a reverse reaction catalyst lowers the activation energy
For both the forward and reverse reaction
As a result the reaction reaches a dynamic equilibrium faster
Enthalpy of combustion
Enthalpy of combustion of a substance is the enthalpy change when ONE MOLE OF FUEL is completely combusted
Enthalpy of solution
The enthalpy change of solution is the enthalpy change when ONE MOLE OF THE SOLUTE (solid) is completely dissolved in water
Enthalpy of neutralisation
The enthalpy change of neutralisation is enthalpy change when ON MOLE OF WATER is formed
What is step 1 in calculating the enthalpy of combustion
Eh=cm🔼T
What is step 2 in calculating the enthalpy of combustion
n= M
—–
GFM
What is step 3 in calculating the enthalpy of combustion
🔼H= Eh
——
n
What does a black deposit of carbon indicate in an enthalpy of combustion reaction
Incomplete combustion
What can incomplete combustion be counteracted with
Bomb calirimeter
What can prevent heat being lost to the surroundings
Heat shield
What increases the accuracy of an experiment
Reputation
What is hess’s law?
States that the enthalpy change of a chemical reaction depends only on the chemical nature and physical state of reactants and products and is independent of any intermediate steps
Enthalpy of combustion
The amount of energy released when 1 mole of a fule is completely burnt in oxygen
Enthalpy of formation
The energy required to form one mole of a substance from its elements in their natural state
What was the average growth of the chemical industry between 1995 and 2000
5 times that of all other manufacturing industries
industrial process are designed to…
Maximise profit and minimise their impact on the environment
Feedstock
A reactant from which other chemicals can be extracted or synthesised to manufacture a required product
Raw material
The original source of feedstock
What are the major raw materials?
Crude oil
Metallic ores and minerals
Air
Water
What are the factors that myst be taken into account when choosing a manufacturing rout
Cost, availability and sustainability of feedstock Yield of product Recyclability of unreacted materials Marketability of by-products Difficulty and cost of wast disposal Energy consumption Atmospheric emissions
What are the environmental factors that must be taken into account when choosing a manufacturing rout
Minimising waste
Avoiding the use or production of toxic substances
Design products that will biodegrade if appropriate
How do manufacturing plants save energy?
Switch to processes requiring less energy
Utilise the heat from exothermic reaction elsewhere
Use waste heat to generate energy
Sell exess energy to supply heating for local housing
REDOX reactions
Reduction and oxidation reaction are occurring simultaneously
If magnesium is loosing e- there for it is being…
Oxidiesed
Metals higher in the ECS ..
Displace metals lower in the electrochemical series from a solution of its ions
Electronegativity indicates
Whether an element will act as an oxidising or reducing agent
Most non metal elements act as…
Oxidising agents
Metals have low electronegativities hence
Act as reducing agents
Oxyanon ions are
Negative ions that contain oxygen combined with other elements
Examples of oxyanion ions
Sulphate ion- SO3^2-
Permanganate ion - MnO4^-
Dichromate ion- CrO7^2-
What is step 1 of calculating the ion equation of redox reactions involving oxyanions
Add H2O to the left to balance the number of oxygen
What is step 2 of calculating the ion equation of redox reactions involving oxyanions
Add appropriate number of H+(aq) ions to the right to balance H
How do you calculate a REDOX reaction
Add the Redox and Oxidation ion electron equations together to form the REDOX equation
The number of electrons in each equation must be the same
Describe chromatography
A small sample of a mixture is placed at the bottom of the chromatography paper and the paper is placed in a suitable solvent
The solvent moves up the chromatography paper by capillary action
Why does separation occur in chromatography
The molecules in the mixture have different polarities and/ or masses
Describe how polarity works in the context of chromatography
Polar solvents dissolve (bond to) polar molecules and carry them further up the chromatography paper than they do non-polar molecules
Describe how mass works in the context of chromatography
The lighter a molecule the further it travels
How do you identify amino acids by chromatography
Hydrolysed amino acids can be identified by chromatography. The hydrolysed amino acids are chromatographed against known amino acids
This process is repeated until all the amino acids in the hydrolysed olysed sample are identified
What is an RF value?
It is common to measure the distance the sample has traveled and compare it with the distance the solvent has traveled, thus calculating a value known as the RF value
RF values are specific for individual molecules in specific solvents
Formula for RF value
X
RF=—-
Y
What is the mobile phase of gas liquid chromatography
An inert gas (ie doesn’t react) like N2 or Ne
What is the stationary phase of gas liquid chromatography
A high boiling point liquid absorbed onto an inert solid that is placed in a long colum
In gas liquid chromatography, each peak represents…
A compound in the mixture
In gas liquid chromatography, the area under the peak is an indication of
the abundance of this compound in the mixture
What is the stationary phase of paper chromatography
The net chromatography paper
What is the mobile phase of paper chromatography
The solvent
Name other forms of chromatography
TLC- Thin layer chromatography
GLS- Gas liquid chromatography
HPLC- high performance liquid chromatography
All identify components in the mixture and the abundance of each compound
