First 6 revision topics

Flashcards based on lecture notes about enthalpy, kinetics, and reaction equilibrium in chemistry.

What is the definition of enthalpy change?

Enthalpy change equals heat change at constant pressure.

Why is the enthalpy of hydration of Ca2+ less exothermic than that of Mg2+?

Ca2+ has a lower charge to size ratio compared to Mg2+.

Is deltaH affected by the moles in the equation?

Yes.

What is the atomisation of SrCl2?

Sr + 2Cl.

What is the atomisation of NaCl?

Na + 1/2Cl2 which becomes Na + Cl.

What should you do when you get bond dissociation enthalpy instead of atomisation?

Divide by 2.

What is always true about the mass numbers of isotopes?

They are always integers.

In a TOF calculation with electrospray ionisation, what adjustment must be made?

Subtract 1 from the mass number to account for the H+.

What is fired from the electron gun in mass spectrometry?

High energy electrons.

Why is it difficult to measure the enthalpy change for thermal decomposition experimentally?

Heating the sample prevents accurate measurement of temperature change.

Why must you use high concentrations for enthalpy change experiments?

To achieve larger temperature changes and reduce uncertainty.

How should you phrase the enthalpy change in calorimetry questions instead of ‘higher than actual value’?

Less exothermic than the true value.

What is the formula for calculating enthalpy change using bond enthalpies?

Reactants - Products.

What is the consequence of particles gaining energy in kinetics?

More molecules have energies greater than or equal to the activation energy.

What must you always do in rates of reaction questions?

Measure temperature at the START and END of a reaction and calculate the mean.

What happens when water is added to an equilibrium mixture?

Equilibrium shifts to the side with the most moles to oppose the change.

What must you always include in answers to equilibrium changes?

Explain why the equilibrium shifted that way - ‘‘to oppose the change in…’’

What is the definition of an oxidising agent?

An electron acceptor.

What is the role of Cl- in the transition from NaCl to HCl?

Cl- acts as a proton acceptor in forming HCl.