Physical Chemistry Flashcards
What PH does the strongest acid have?
0PH
What PH does the strongest alkali have?
14PH
What PH is neutral (water)
7PH
What does an indicator do?
Change colour to show the PH of a solution
What colours does universal indicator show?
Acidic: Red
Neutral: Green
Alkali: Purple
What colours does litmus paper show?
Acidic: Red
Neutral: Purple
Alkali: blue
What colours does phenolphthalein show?
Acidic: Colourless
Alkaline: Pink
What colours does Methyl orange show?
Acidic: red
Alkaline: yellow
What’s an acid?
Source of hydrogen ions (H+) with a PH less than 7
What’s a base?
A substance which can neutralise an acid
What’s an alkali?
Soluble base with a source of hydroxide ions, (OH-) and PH greater than 7
What’s a neutralisation reaction?
Acid + Base = salt + water, or H+ + OH- = H2O
What PH are the products after a neutralisation reaction?
7 neutral
What’s the equation when an acid and a metal oxide react?
Acid + metal oxide = Salt + water
If the acid is hydrochloric acid what will the metal salt be?
A chloride
If the acid is Sulphuric acid what will the metal salt be?
A sulphate
If the acid is Nitric acid what will the metal salt be?
A nitrate
What’s the equation for an acid and a metal Carbonate?
Acid + Metal Carbonate = Salt + water + Carbon dioxide
What does soluble mean?
Can dissolve in water
What does insoluble mean?
Can’t dissolve in water
Which salts are soluble?
All except carbonates (few exceptions)
How do you make a soluble salt with an acid and an insoluble base?
Mix the acid (Nitric acid), and insoluble base (copper carbonate) They will produce crystals, filter and evaporate them
How do you make an insoluble salt?
A precipitation reaction
What’s a precipitation reaction?
Mixing 2 solutions with ions you require, to make an insoluble salt and eg barium chloride + Sulphuric acid= Barium Sulphate + hydrochloric acid
What are titrations used for?
To find out how much acid is needed to neutralise an alkali (or vice versa)
Method for a titration?
Add alkali to a conical flask with an indicator
Put acid in a burette and add to the alkali until there’s the required colour change, and measure how much was used
How to work out the concentration from a titration calculation?
Work out the moles of the substance you have
Write the equation for the reaction, and compare the ratio to work out the amount of moles in unknown substance
Work out the concentration of the unknown stuff
What’s a slow reaction?
Rusting
What’s a moderate reaction?
Magnesium reacting with acid
What’s a fast reaction?
An explosion
What does the rate of reaction depend on?
Temperature
Concentration (or pressure for gasses)
Catalyst
Size of particles (surface area)
Formula for rate of reaction?
Rate of reaction= Amount of reactant used or amount of product formed / Time
What’s the precipitation method of measuring a rate of reaction?
When the product is a precipitate which clouds a solution and you measure how long until you can’t see through the solution
What’s the change in mass method of measuring a rate of reaction?
Place the reaction on scales and measure how the mass drops as the reaction goes on
What’s the measuring volume of gas given off method in measuring the rate of reaction?
Use a gas syringe to measure the amount of gas given off during the reaction
What’s a way of proving that bigger surface area means faster reaction?
React hydrochloric acid with marble chips, with different size chips, and notice the smaller chips produce more gas
Why does a larger surface area increase the rate of reaction?
More frequent collisions
What’s a method to prove that a higher concentration of acid increases the rate of reaction?
React magnesium metal with dilute HCL, and see when the acid is a higher concentration the mass drops down faster
How to show how temperature effects the rate of reaction?
Sodium Thiosulfate and HCL produce a cloudy precipitate, so see how long it takes until you can’t see through the flask
How to show how a catalyst effects the rate of reaction?
Via the decomposition of hydrogen peroxide into water, add manganese to see it increase the rate of reaction
What’s collision theory?
States that the rate of reaction, depends on how hard and how often the reacting particles collide
How does a higher temperature increase the rate of reaction?
Particles have more energy so move quicker, so they collide more often
How does a Higher concentration ( or pressure) increase the rate of reaction?
Particles closer together so the important particles will collide and react more often
How does a larger surface area increase the rate of reaction?
The particles will have more area to react with, so there will be more successful collisions
How does a catalyst increase the rate of reaction?
Gives the reacting particles an area to stick to
Increasing the successful collisions by lowering the activation energy
What causes faster collisions?
Hot temperature
Why does a hot temperature cause faster collisions and more successful ones?
Particles have more energy so move faster, and have enough energy to make the reaction happen
What happens in a chemical reaction?
Old bonds broken, new bonds made
What process is bond breaking?
Endothermic, as energy is supplied to make the bonds
What process is bond making?
Exothermic as energy is released when new bonds are formed
What’s an exothermic reaction?
Gives out energy, in the form of heat, shown by a rise of temperature in the surroundings
So the bond formation is energy is greater than bond breaking energy
What’s an endothermic reaction?
Takes in energy, in the form of heat, shown by a fall of temperature in the surroundings
So the bond formation is energy is smaller than bond breaking energy
What’s the overall change in energy in a reaction called?
The enthalpy change ( Delta H)
What unit is Delta H?
kj/mol
If Delta H is Negative then the reaction is?
Exothermic as heat is given out
If Delta H is positive then the reaction is?
Endothermic, as heat is taken in
Pointers for Exothermic reaction graph?
Reactants higher than products
Difference in height shows energy change
The initial shows the activation energy
What’s the activation energy?
The energy required to break the old bonds
Pointers for an endothermic graph?
Reactants lower than products
Difference in height shows energy change
What are the axis on an energy level diagram?
X= Progress of reaction Y= Energy
How do catalysts reduce the activation energy?
They give an alternative reaction pathway
What’s the formula for finding enthalpy change?
Enthalpy change Delta H = Total energy absorbed breaking bonds - total energy released making bonds
Method for finding the Enthalpy change?
Draw out the molecules already there and the molecules made, and using the table work out the total energies
Use enthalpy change equation
Experiment to work out enthalpy change?
Calorimetry
What’s calorimetry used to work out energy transferred in neutralisation, dissolving and displacement reactions
?
Measure the heat of the reagents, then the heat of the solution, whilst insulating it
What’s combustion calorimetry?
Burn a fuel to see how much fuel it takes to heat water to 50C
Use copper can, and reduce draughts to make it more accurate
Equation for energy transferred, in calorimetry?
Energy transferred (joules) = mass of water g x temp change C x 4.2 (energy to heat 1 g of water by 1C)
Method for working out energy transferred?
Work out all the things required for the energy transferred equation
Use the energy transferred equation
Work out the mass of fuel used, and work out how much energy whatever mass of the fuel produces
What’s the molar enthalpy change?
The enthalpy change given out by one mole of the reactant
How to work out the molar enthalpy change?
Calculate the amount of energy transferred
Work out the moles of fuel produced the heat by using the mass and Mr
Then divide the energy change (if it was exothermic this number will be negative) by the amount of moles to find the Kj/mol
What’s a reversible reaction?
Where the products of one reaction, can themselves react to make the original reactents
What’s an example of a reversible reaction?
Thermal decomposition of ammonia chloride (S)
Breaks down to make ammonia (G) and hydrogen (G) chloride
Which can then re form to make ammonia chloride
What’s dynamic equilibrium?
Where the forward and backward reactions are equal so the overall effect is nil, happens in a closed sytem (no product can escape)
What are all reactions in directions?
Endothermic one way, endothermic the other way
How does increasing the temperature effect the reaction?
Endothermic increases to use extra heat up
How does reducing the temperature effect the reaction?
Exothermic increases to give more heat out
What’s the position of equilibrium?
The relative amount of products and reactents
What do all gaseous reactions have?
More molecules on one side than the other
How does raising the pressure effect the reaction?
Encourages the reaction which produces fewer molecules of gas
How does decreasing the pressure effect the reaction?
Encourages the reaction which produces more molecules of gas
