Question

1) What volume of 17.4 M acetic acid should be used to produce 0.100 L of 3.00 M acetic acid solution?

2) Given the following thermochemical equation, how much total energy is released when 1.50 kg of CH₄ is combusted?:
CH₄ (g) + 2O₂ (g) -----> CO₂(g) + 2H₂O (l)

Thank you!!

Answer 1

1) Given:

Molarity of acetic acid M₁ = 17.4 M

The volume of acetic acid V₂ = 0.100 L

Molarity of acetic acid M₂ = 3.00 M

Solution:

To find the volume used to produce 0.100 L of 3.00 M acetic acid solution from a stock solution:

The formula M₁V₁ = M₂V₂ where “1” represents the concentrated conditions and “2” represents the diluted conditions.

V₁ = M₂V₂/ M₁

V₁ = (3.00M*0.100L)/17.4 M

V₁ = 0.01724 L

V₁ = 17.24 mL

17.24 mL of 17.4 M acetic acid should be used to produce 0.100 L of 3.00 M acetic acid solution

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2) Given the thermochemical equation:

CH₄ (g) + 2O₂ (g) → CO₂(g) + 2H₂O (l)

The heat of reaction = [the sum of all heats of formation of all products] - [the sum of all heats of formation of all reactants]

The calculation for the heat of combustion for methane is

The heat of combustion of CH₄= [heat of formation of CO₂(g) + 2 * heat of formation of H₂O (l)] –

            [heat of formation of CH₄ (g) + 2 * heat of formation of O₂ (g)]

Heat of combustion of CH₄= [-393.5 kJ/mol + 2 * (-285.8 kJ/mol)] – [-74.8 kJ/mol + 2 * (0 kJ/mol)]

Heat of combustion of CH₄= [-393.5 kJ/mol + (-571.6 kJ/mol)] – [-74.8 kJ/mol + (0 kJ/mol)]

Heat of combustion of CH₄= - 965.1 kJ/mol + 74.8 kJ/mol = -890.3 kJ/mol

Negative sign indicates heat is released.

One mole of methane release 890.3 kJ

Calculate the number of moles in 1.50 kg of methane

Molar mass of methane = 16.04 g/mol

Mass of methane = 1.50 kg = 1500 g

Moles of methane = mass of methane / Molar mass of methane

Moles of methane = 1500 g / 16.04 g/mol

Moles of methane = 1500 g / 16.04 g/mol = 93.5162 mol

One mole of methane produces 890.3 kJ of energy

93.5162 moles of methane produce = (890.3 kJ * 93.5162 mol)/1 mol = 83257.4729 kJ

83257.4 kJ of energy released from 1.50 kg of methane is combusted.

Round off three significant figures, then 83300 kJ heat produced.

83300 kJ of energy released from 1.50 kg of methane is combusted.