Topic 8-Thermodynamics Flashcards

1
Q

What is an exothermic reaction explain in energy and bonds?

A

Energy is being released to the surroundings and this means bonds are being formed
An example of exo is combustion

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2
Q

What is endothermic reactions in energy and bonds?

A

Endothermic reactions are when energy is taken in and this means bonds are being broken
Photosynthesis is an example

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3
Q

What is the first law of thermodynamics?

A

Energy can neither be created or destroyed but transferred from one to another

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4
Q

What is activation energy?

A

Minimum amount of energy required for a reaction to occur

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5
Q

What is the formula for Total energy for reactants?

A

Total EOR=Total EOP + energy lost or gained

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6
Q

What is enthalpy?

A

Measure of heat content of a substance at a constant temperature

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7
Q

Explain the relationship between stoichiometry and enthalpy?

A

Enthalpy is directly proportinal to stochiometry
If all moles of substance are doubled than Enthalpy is doubled

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8
Q

Define standard enthalpy of formation?

A

One mole of a substance is formed in its standard state from its elements in their standard states

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9
Q

What is standard enthalpy of combustion?

A

When one mole of a substance undergoes complete combustion under standard conditions
Where all reactants and products are in their standard states

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10
Q

What is calorimetry?

A

Involves the practical determination of enthalpy changes usually involves heating or cooling known amounts of water

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11
Q

Equation for heat energy?

A

Energy=mass×SHC×change in temp

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12
Q

Explain some inaccuracies due to calorimetry?

A

Heat lost to surroundings-not all heat is transferred to fuel
Incomplete combustion-fuel may not burn properly
Evaporation of fuel-some fuels evaporates instead of combusting
Heat absorbed by calorimeter

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13
Q

Explain the process of Measuring the Change in Temperature?

A

Temp is taken every 30s for 3 min to ensure the change in temp is constant
Reactants are mixed after 3 mins
Let reaction complete
Further readings taken every 30s as reaction cools,so change in temp is decreasing
We extrapolate to calculate value of change in temp

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14
Q

Why do we extrapolate the graph when measuring change in temperature?

A

We extrapolate as energy is being lost due to ongoing reaction,so by extrapolating the graph so its perpendicular to constant temp,we mitigate this and make it more accurate

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