Reactivity 2.1 Flashcards
What occurs in a chemical reaction?
No overall change in mass. Energy change due to reactant bonds broken and new bonds formed.
Relationship between reactant particles and number of product particles
It is fixed (known as stoichiometry)
Ionic equations
Used to show the ions that react and the spectator ions that are left out.
Half equation
When a change in oxidation state occurs, it can be useful to write the half equation
Gas volume is determined by…
The number of particles and the temperature/pressure
Avogadro’s Law
Equal volumes of the same gas under the same conditions of temperature and pressure contain equal numbers of molecules
Molar volume
Volume occupied by one mole of gas. It is the same for all gases when measured under the same temp/pressure
The concentration of a solution can be calculated by…
Titrating it with a standard solution with a known concentration
cm^3 -> dm^3
/ 1000
cm^3 -> m^3
/ 1000 /1000
When is a back titration used?
Used when the end point is hard to identitfy or when one reactant is impure
Back titration
A known excess of one of the reactants is added to the reaction mixture. Unreacted excess is determined by the titration against the standard solution. By subtracting the amount of unreacted reactant from the original amount used, the reacting amount can be determined.
All gases under the same condition…
Have the same molar volume
The mole ratio of an equation can be used to determine…
The concentrations of reactants and products in solutions
Summary of how to solve an equation
- Write a balanced equation
-For the given reactant find n (n=cv) - Use the answer and mole ratio to find moles of other reactant
- Calculate c using c=n/V
Limiting regeant
The reactant that runs out first - this determines the amount of product formed
Theoretical yield
Maximum amount of product that could be formed according to the balanced equation
Experimental yield
Actual amount of product obtained when experiment is preformed
Percentage yield
(Experimental yield/theoretical yield) x 100
Why would the experimental yield be lower than the theoretical? (5)
- Incomplete reaction
- Reversible chemical reactions preventing process completion
- Side reactions occurring
- Decomposition of reactants or products
- Loss of product during purification
(IRS DL)
Why would the experimental yield be higher than the theoretical yield?
- Impurities in a product
- When a product has not been fully dried
Standard solution
Solution of known concentration
Acid-base titration
Titrated against a standard solution to determine concentration. When indicator changes colour, indicates the equivalence point
Equivalence point
Where the stoichiometric amounts of acid and base have reacted completely
Green chemistry
Seeks to minimise production and release to the environment of hazardous substances
Formula for atom economy
= (mass of desired product/mass of actual products) x 100
Atom efficient reactions
Addition polymerisation and hydrogenation of alkenes (high yield, no solvents, no by-products)
