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steposvetlana [31]
3 years ago
15

A scientist measures the standard enthalpy change for the following reaction to be -327.2 kJ : P4O10(s) 6 H2O(l)4H3PO4(aq) Based

on this value and the standard enthalpies of formation for the other substances, the standard enthalpy of formation of P4O10(s) is kJ/mol.
Chemistry
1 answer:
OleMash [197]3 years ago
5 0

Answer:

ΔH°f P4O10(s) = - 3115.795 KJ/mol

Explanation:

  • P4O10(s) + 6H2O(l) ↔ 4H3PO4(aq)
  • ΔH°rxn = ∑νiΔH°fi

∴ ΔH°rxn = - 327.2 KJ

∴ ΔH°f H2O(l) = - 285.84 KJ/mol

∴ ΔH°F H3PO4(aq) = - 1289.5088 KJ/mol

⇒ ΔH°rxn = (4)(- 1289.5088) - (6)(- 285.84) - ΔH°f P4O10(s) = - 327.2 KJ

⇒ ΔH°f P4O10(s) = - 5158.035 + 1715.04 + 327.2

⇒ ΔH°f P4O10(s) = - 3115.795 KJ/mol

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<u>Answer:</u> The molality and molarity of zinc in the solution is 4.07 m and 28.11 M respectively.

<u>Explanation:</u>

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As, zinc is present in smaller proportion. So, it is solute and copper is the solvent.

  • <u>Calculating molality of zinc:</u>

To calculate molality of the zinc, we use the equation:

Molality=\frac{m_{solute}\times 1000}{M_{solute}\times W_{solvent}\text{ in grams}}

where,

m_{solute} = Given mass of solute (Zinc ) = 21 g

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Putting values in above equation, we get:

\text{Molality of Zinc}=\frac{21\times 1000}{65.3\times 79}\\\\\text{Molality of zinc}=4.07m

  • <u>Calculating molarity of zinc:</u>

To calculate volume of a substance, we use the equation:

\text{Density of substance}=\frac{\text{Mass of substance}}{\text{Volume of substance}}

Density of solution = 8740kg/m^3=\frac{8740kg\frac{1000g}{1kg}}{1m^3\times \frac{10^6cm^3}{1m^3}}=\frac{8740g}{1000cm^3}=8.740g/cm^3

(Conversion factors used are:  1 kg = 1000 g &  1m^3=10^6cm^3  )

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Putting values in above equation, we get:

8.740g/cm^3=\frac{100.0g}{\text{Volume of zinc}}\\\\\text{Volume of zinc}=11.44cm^3

To calculate the molarity of solution, we use the equation:

\text{Molarity of the solution}=\frac{\text{Mass of solute}\times 1000}{\text{Molar mass of solute}\times \text{Volume of solution (in mL)}}

We are given:

Molar mass of zinc = 65.3 g/mol

Volume of solution = 11.44cm^3=11.44mL     (Conversion factor:  1cm^3=1mL  )

Mass of zinc = 21.0 g

Putting values in above equation, we get:

\text{Molarity of zinc}=\frac{21\times 1000}{65.3\times 11.44}=28.11M

Hence, the molality and molarity of zinc in the solution is 4.07 m and 28.11 M respectively.

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