What is the formula to calculate number of moles?
No. of moles = mass / molar mass
How can volume of gas be measured?
- gas syringe
- upturned measuring cylinder or burette
How can mass of gas be measured?
Weigh the reaction container before the experiment and after the experiment. The change in mass is the mass of the gas.
Calculate the number of moles of a known concentration of gas given the volume at room temperature and pressure.
Number of moles = concentration X volume
How does the volume of gas produced during the course of a reaction change?
The volume of gas produced increases during the course of a reaction.
What happens in a reversible reaction at equilibrium?
- the rate of the forward reaction equals the rate of the backward reaction
- the concentrations of the reactants and products do not change
Explain why a reversible reaction may reach an equilibrium.
When the reaction takes place in a closed system, the rate of forward reaction decreases and the rate of backward reaction increases until eventually the rate of forward reaction equals the rate of backward reaction. Which is when equilibrium is reached.
What are the factors which affect the position of equilibrium?
- removing a product moves the position of equilibrium to the right
- adding extra reactant moves the position of equilibrium to the right
- increasing temperature moves the position of equilibrium in the direction of the endothermic reaction
- increasing pressure moves the equilibrium to the side with the least number of moles of gas molecules
Write the balanced symbol equation for the reversible reaction between Sulfur dioxide and oxygen in the Contact Process.
2SO2 (g) + O2(g) —–> 2SO3 (g)
Explain the conditions in the Contact Process.
- 450 degrees Celsius
Increasing temperature moves equilibrium to the left and increases rate of reaction. - Atmospheric Pressure
At low pressure, equilibrium is already on the right, so expensive high pressure is not needed. - Vanadium Pentoxide Catalyst
Increases rate of reaction but doesn’t change position of equilibrium.
What is the word equation for the reaction between Barium Chloride and Sodium Sulfate?
Barium Chloride + Sodium Sulfate —–> Barium Sulfate + sodium chloride
How do acids ionise in water?
Strong acids completely ionise in water. Weak acids do not fully ionise and forms an equilibrium mixture.
Explain why the pH of a weak acid is much higher than the pH of a strong acid of the same concentration?
Strong acids have a lower pH than weak acids of the same concentration. This is because, strong acids completely ionise in solution. Weak acids only partially ionise in water.
Explain the difference between acid strength and acid concentration?
Acid strength is a measure of the degree of ionisation of the acid. Acid concentration is a measure of the number of moles of acid in one dm^3.
Explain why ethanoic acid reacts slower than hydrochloric acid of the same concentration?
Ethanoic acid has a lower concentration of hydrogen ions, therefore, in ethanoic acid, the hydrogen ions have a lower collision frequency with reactant particles.
Explain why Ethanoic Acid is less conductive than Hydrochloric Acid of the same concentration?
There is a lower concentration of hydrogen ions in ethanoic acid to carry the charge.
Explain, in terms of collisions between ions, why most precipitation reactions are extremely fast?
The collision frequency between ions in solution is very large. There is a high chance that different ions will collide with each other and cause a reaction.
What is aqueous Barium Chloride used to test for ?
Sulfate ions (white precipitate)
What is aqueous Lead Nitrate used to test for?
- Chloride ions (white precipitate)
- Bromide ions (cream precipitate)
- Iodide ions (yellow precipitate)
Write the ionic equation for the precipitation reaction between Barium Chloride and Sodium Sulfate (give state symbols)?
Ba^2+ (aq) + SO4^2-(aq) ——> BaSO4(s)
What are ‘spectator ions’ ?
Ions that are present in a reaction mixture but not involved in the reaction.
What are the stages involved in the preparation of a dry sample of an insoluble compound by precipitation?
- Mix solution of reactants
- Filtration
- Wash and dry residue
Calculate the amount in moles of a volume of gas at rtp given the molar gas volume at rtp.
Amount of gas(moles)=volume of gas at rtp/molar volume at rtp
Molar volume = 24dm^3
