Concept explainers
(a)
Interpretation:
Number of moles of
Concept introduction:
Number of moles can be determined using the given equation,
Here, n is the number of moles
M is the Molar mass
m is the Mass
(a)
Answer to Problem 5.90QE
Explanation of Solution
Mass of one mole of water gas is
Number of moles of water gas is determined as follows,
Ratio of
Number of moles of
(b)
Interpretation:
Enthalpy change when
Concept introduction:
According to Hess’s Laws, change in enthalpy in an overall reaction can be calculated from the change in enthalpy of other reactions.
- If an equation is obtained by the addition of more than one thermochemical equations, then the enthalpy change of that equation is the sum of change in enthalpy of all the equations added.
- If an equation is the reverse direction of a thermochemical equation, then the change in enthalpy has same numerical value but opposite sign.
- The enthalpy change depends on the mass of reacting substance. If the coefficients present in an equation is multiplied with a factor, then change in enthalpy also should be multiplied with that same factor.
(b)
Answer to Problem 5.90QE
Enthalpy change when
Explanation of Solution
Mass of one mole of water gas is
Number of moles of water gas is determined as follows,
Given reactions are shown below,
Balanced chemical equation for the burning of water gas in air is shown below,
From the above equations, it is clear equation (3) can be obtained by adding equation (1) divided by 2 and equation (2) divided by 2.
According to Hess’s Law, when the direction of reaction reverses, then the enthalpy change will get opposite sign. Also, when the number of reactants and products are multiplied or divided by a factor, then the enthalpy change must also be multiplied or divided by the same factor.
Enthalpy change for the combustion of 1 mole of water gas is
Enthalpy change when
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Chapter 5 Solutions
Chemistry: Principles and Practice
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