C3 Part B Flashcards
What is the numerical form of a “mole”? Give it in standard form
6.023 x 1023
How many atoms of carbon-12 weigh exactly 12g?
6.023 x 1023
(A mole)
Fill in the gaps:
A mole of ………. of any element or compound weighs the same number of ………… as the ……………… (Ar) of the element or compound.
A mole of atoms/molecules of any element or compound weighs the same number of grams as the relative atomic mass (Ar) of the element or compound.
Give two possible units that concentration of a substance can be measured in
moles per dm3
grams per dm3
1 litre = 1000 cm3 = 1 dm3
Fill in the gaps:
The …….. solute you dissolve in a given volume, the more crowded the solute ……. are and the …… ……….. the solution.
The more solute you dissolve in a given volume, the more crowded the solute molecules are and the more concentrated the solution.
What kind of experiment is used to measure how much acid is needed to neutralise an alkali?
Titration
Describe the process of a titration
- Put an alkali in a flask, along with indicator (phenolphthalein or methly orange)
- Add the acid to the alkali a little bit at a time using a burette, giving the flask a regular swirl
- When the indicator changes colour, it means all the alkali has ben neutralised
- Record the amount of acid needed to neutralise the alkali
What are the two main titration equations? Draw the equation pyramid if it helps
- Number of moles = Concentration (moles/dm3) x Volume (dm3)
- Mass in grams = Number of moles x Relative formula mass

Fill in the gaps
An exothermic reaction is one that gives out …….. to the surroundings, usually in the form of ……. and shown by a ……… in temperature.
An ………… reaction in one which takes in energy from the ……….., usually in the form of heat and shown by a …… in temperature.
An exothermic reaction is one that gives out energy to the surroundings, usually in the form of heat and shown by a rise in temperature.
An endothermic reaction in one which takes in energy from the surroundings, usually in the form of heat and shown by a fall in temperature.
Energy must be supplied to break existing bonds, so bond breaking is what kind of reaction?
Endothermic
Energy is released when new bonds are formed, making it what kind of reaction?
Exothermic
Fill in the gaps:
In an endothermic reaction, the energy required to break old bonds is ……… than the energy ……….. when new …….. are formed.
In an ………. reaction, the energy released in bond ……….. is greater than the energy used in ……… old bonds.
In an endothermic reaction, the energy required to break old bonds is greater than the energy released when new bonds are formed.
In an exothermic reaction, the energy released in bond formation is greater than the energy used in breaking old bonds.
How can energy transfer be measured in endothermic/exothermic reactions?
By measuring temperature change.
What are the issues with the fuels we currently use and have relied on for decades to provide energy?
- Burning fuels releases CO2 and contributes to the greenhouse effect, causing a rise in global temperature and thermal expansion of the seas to occur
- Developing alternative, renewable sources of energy costs losts of money
- Crude oil is a finite resource
- The transportation of oil, which can only be found in certain places on earth, costs money and causes harmful emissions to be released.
By what process is fuel energy calculated?
Calorimetry
Outline the process of calorimetry
- Put a defined amount of water in a copper can and record its temperature
- Weigh the spirit burner and the lid that is being used
- Put the spirit burner underneath the can and light the wick. Heat the water, stirring constantly until the temperature reaches about 50°C.
- Put out the flame, using the burner lid and measure the dinal temperature of the water.
- Weigh the spirit burner and the lid again.
(almost exactly the same process can be used to calculate the amount of energy produced by food)
What is the equation for working out energy transfer in calorimetry?
Q = mcΔT
Energy transferred (joules) = Mass of water (grams) x Specific heat capacity of water (4.2) x Temperature change (in °C)
What is the main difference between the energy level diagrams of endothermic and exothermic reactions?
In exothermic reactions, the products are at a lower energy than the reactions, whereas in endothermic reactions the products are at a higher energy than the reactants.
Draw and annotate sketches of energy level diagrams for endothermic and exothermic reactions

What is the activation energy of a reaction?
The minimum energy required for reeacting particles to break their bonds
How can the activation energy of a reaction be lowered and how is this represented on an energy level diagram?
A catalyst can be addes so that the reaction occurs more easily and more quickly. This will be evident on an energy level diagram by a lower curve.
Note: The overall energy change for the reaction remains the same
What are the bond energies applied to:
H-H
Cl-Cl
H-Cl
H-H = 436 kj/mol
Cl-Cl= 242 kj/mol
H-Cl = 431 kj/mol
How much energy is required to break one mole of H-H and one mole of Cl-Cl bonds?
(H-H = 436 kj/mol
Cl-Cl= 242 kj/mol)
436 + 242 = 678 kj
How much energy does forming two moles of H-Cl release?
2 x 431 = 862 kj