Chem q Flashcards

1
Q

Explain how the abundance of an isotope is measured.

A

Detector, Current related to abundance

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2
Q

Catalyst

A

Increases rate of chemical reaction without being used up

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3
Q

Along period 2, which element deviates in the trend in ionisation energy and why?

A

Oxygen, as it has electron pair in the p orbital so repulsion occurs.

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4
Q

What element in period 2 has the highest 2nd ionisation energy?

A

Lithium

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5
Q

What is a dynamic equilibrium?

A

Where rates of forwards and backwards reactions are the same. Concentrations are constant.

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6
Q

What is Hess’s law?

A

That the enthalpy change of a reaction at constant pressure is independent of the route taken.

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7
Q

H2C=CH2(g) + H2O(g) CH3CH2OH(g)

Identify the catalyst used in this reaction

A

H3PO4 or H2SO4

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8
Q

Write an equation, including state symbols, for the reaction that has an enthalpy change that is the standard enthalpy of formation of ethanol.

A

2C(s) + 3H2(g) + ½O2(g) —> CH3CH2OH(l)

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9
Q

Suggest why the experimental value is different from data book value.

A

Mean bond enthalpies are an average from a range of compounds

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10
Q

State why the standard enthalpy of formation for oxygen gas is zero.

A

It is an element

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11
Q

Define enthalpy of solution.

A

Enthalpy change when 1 mole of solid dissolves completely in water to give a solution of infinite dilution at constant pressure.

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12
Q

Define enthalpy of hydration.

A

Enthalpy change when 1 mole of gaseous ions dissolve in sufficient water to give an infinitely dilute solution. Hydration enthalpies are always negative.

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13
Q

Give two features of a reaction at equilibrium.

A
  • Concentrations stay constant

- Forward rate = backward rate

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14
Q

Why does a catalyst have no effect on equilibrium?

A

Speeds up reaction on both sides, increases rate.

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15
Q

Define mean bond enthalpy.

A

Enthalpy needed to break a bond, averaged over different molecules.

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16
Q

Define enthalpy of formation

A

enthalpy change when one mole of a compound is formed from its elements in their standard states

17
Q

Why does gibbs free energy change for the formation of Nitrogen monoxide stay constant at different temperatures?
N2 + O2 → 2NO

A

Number of molecules is the same of either side. So entropy stays constant.

18
Q

Enthalpy of lattice formation

A

Enthalpy change when one mole an ionic substance is formed from its ions in gaseous state.

19
Q

Explain the interactions between water molecules when F- becomes hydrated.

A

Water is polar and positive H are attracted by F– ions

20
Q

Why is pure water not acidic?

A

[H+] = [OH–]

21
Q

Buffer solution

A

Maintains a constant pH, despite the addition of small amounts of acid or alkali.