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Ghella [55]
4 years ago
5

Two mixtures were prepared from three very narrow molar mass distribution polystyrene samples with molar masses of 10,000, 30,00

0 and 100,000 g/mola indicated below: (A) Equal numbers of molecules of each sample (B) Equal masses of each sample. For each of the mixtures, calculate the number-average and weight-average molar masses and comment upon the meaning of the values.

Chemistry
1 answer:
AnnZ [28]4 years ago
7 0

Answer:

Hello some parts of your question is missing

Two mixtures were prepared from three very narrow molar mass distribution polystyrene samples with molar masses of 10,000, 30,000 and 100,000 g mol−1 as indicated below: (a) Equal numbers of molecules of each sample (b) Equal masses of each sample (c) By mixing in the mass ratio 0.145:0.855 the two samples with molar masses of 10,000 and 100,000 g mol−1 For each of the mixtures, calculate the number-average and weight-average molar masses and comment upon the meaning of the values.

Answers:

a) 46.666.66 g/mol

b) 20930.23 g/mol

c)43333.33 g/mol

Explanation:

A)The equal number of molecules of each sample can be calculated using  Mn = \frac{n(M1 + M2 + M3)}{3n}

because for the number of molecules to be equal : n1 = n2 = n3 = n

Mn = 46666.66 g/mol

B ) To calculate the equal masses of each sample

we apply this equation

Mn = \frac{W1 + W2 +W3}{\frac{W1}{M1} +\frac{W2}{M2}+ \frac{W3}{M3}  }

ATTACHED BELOW IS THE REMAINING PART OF THE SOLUTION

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Considering the Hess's Law, the enthalpy change for the reaction is -906.4 kJ/mol.

<h3>Hess's Law</h3>

Hess's Law indicates that the enthalpy change in a chemical reaction will be the same whether it occurs in a single stage or in several stages. That is, the sum of the ∆H of each stage of the reaction will give us a value equal to the ∆H of the reaction when it occurs in a single stage.

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You know the following reactions, with their corresponding enthalpies:

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Equation 2:  2 N₂ + 2 O₂ → 4 NO     ΔH = 361.1 kJ/mol

Equation 3: 2 H₂ + O₂→ 2 H₂O     ΔH = -483.7 kJ/mol

Because of the way formation reactions are defined, any chemical reaction can be written as a combination of formation reactions, some going forward and some going back.

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