Chemical Reactions and Heat Energy Quiz

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According to the first law of thermodynamics, what is the relationship between internal energy change (ΔE), heat (q), and work (w) for a system?

ΔE = w - q

ΔE = q - w (correct)

ΔE = -q - w

ΔE = q + w

Which of the following is the correct definition of enthalpy (H) in thermodynamics?

H = E - 2PV

H = PV - E

H = E + PV (correct)

H = E - PV

In a constant pressure process, the heat absorbed by a system is equal to the change in:

volume (ΔV)

internal energy (ΔE)

pressure (ΔP)

enthalpy (ΔH) (correct)

The calorific value of a fuel is defined as:

the amount of heat released when one mole of the fuel is burned completely in oxygen Signup and view all the answers

The heat of reaction (ΔH) for a chemical reaction is equal to:

the difference between the enthalpies of the reactants and products Signup and view all the answers

In an isothermal process, the change in internal energy (ΔE) of a system is:

always zero Signup and view all the answers

What is the relationship between ΔH and ΔE in a chemical reaction?

ΔH = ΔE + PΔV Signup and view all the answers

What is the significance of the heat of reaction in a chemical equation?

It represents the negative of the enthalpy change of the reaction. Signup and view all the answers

What is the unit of heat of reaction (ΔH)?

Kilocalories Signup and view all the answers

Why are the calorific values of gaseous fuels usually determined in constant volume calorimeters?

To avoid the additional energy of expansion Signup and view all the answers

What is the value of q in a constant volume calorimeter?

q = ΔE Signup and view all the answers

What is the value of ΔH for the reaction H2(g) + F2(g) → H2F2 (g) if ΔE = – 14.2 kcal/mole at 25º C?

ΔH = ΔE - RT Signup and view all the answers

According to the first law of thermodynamics, what is the change in internal energy (ΔE) for a process where a system absorbs 400 J of thermal energy from its surroundings?

906 J Signup and view all the answers

What is the maximum work done when pressure on 10 g of hydrogen is reduced from 20 to one atmosphere at a constant temperature of 273 K, given that the gas behaves ideally?

-8126.65 cals Signup and view all the answers

Will there be any change in internal energy (ΔE) when the pressure on 10 g of hydrogen is reduced from 20 to one atmosphere at a constant temperature of 273 K?

No, ΔE = 0 Signup and view all the answers

What is the heat content (q) of the system in a process where the pressure on 10 g of hydrogen is reduced from 20 to one atmosphere at a constant temperature of 273 K?

-8126.65 cals Signup and view all the answers

What is the enthalpy (H) of a system at constant pressure?

The internal energy (E) plus the PV energy Signup and view all the answers

What is the difference between the heat content and enthalpy of a system?

Heat content is the same as internal energy (E) at constant volume, while enthalpy is the same as internal energy (E) plus PV energy at constant pressure Signup and view all the answers