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Determine the molecular formulas of these compounds:

1. An empirical formula of P2O5 and a molecular mass of 310 g/mol

2. The ratio of carbon atoms to hydrogen atoms to oxygen atoms in a molecule is 1 to 2 to 1. What is its molecular formula if its molar mass is 200.18 g/mol?

Sagot :

whitneytr12

The molecular formulas of the empirical ones of P₂O₅ and CH₂O are P₄O₁₀ and C₇H₁₄O₇, respectively, knowing that their molar masses are 310 and 200.18 g/mol, respectively.  

1. Molecular formula of P₂O₅

We can calculate the molecular formula as follows:

[tex] MF = n*EF [/tex]   (1)

Where:

  • MF: is the molecular formula
  • EF: is the empirical formula
  • n: is an integer  

To calculate the integer n, we need to use the following equation:

[tex] n = \frac{M}{M_{EF}} [/tex]   (2)

Where:

  • M: is the molar mass of P₂O₅ =  310 g/mol
  • [tex]M_{EF}[/tex]: is the molar mass of the empirical formula

The molar mass of the empirical formula of P₂O₅  is given by:

[tex]M_{EF} = 2A_{P} + 5A_{O}[/tex]

Where:

  • [tex]A_{P}[/tex]: is the atomic weight of phosphorus = 30.974 g/mol
  • [tex]A_{O}[/tex]: is the atomic weight of oxygen = 15.999 g/mol

So, the molar mass of the empirical formula of P₂O₅  is:

[tex] M_{EF} = (2*30.974 + 5*15.999) g/mol = 141.943 g/mol [/tex]  

Now, we can find the integer n (eq 2).

[tex] n = \frac{M}{M_{EF}} = \frac{310 \:g/mol}{141.943 \:g/mol} = 2 [/tex]  

Finally, after multiplying the integer n by the number of atoms on the empirical formula of P₂O₅, we have (eq 1):

[tex]MF = n*EF = 2 \times P_{2}O_{5} = P_{(2 \times 2)}O_{(5 \times 2)} = P_{4}O_{10}[/tex]

Therefore, the molecular mass of P₂O₅ is P₄O₁₀.

2. Molecular formula of CH₂O  

We know:

  • M: molar mass of CH₂O = 200.18 g/mol

To calculate the integer n and so the molecular mass of the molecule, we need to calculate the molar mass of the empirical formula of CH₂O.

[tex]M_{EF} = A_{C} + 2A_{H} + A_{O} = (12.011 + 2*1.008 + 15.999) g/mol = 30.026 \:g/mol[/tex]

 

Now, the integer n is equal to (eq 2):

[tex] n = \frac{M}{M_{EF}} = \frac{200.18 g/mol}{30.026 g/mol} \approx 7 [/tex]

Finally, the molecular formula of the molecule is (eq 1):

[tex]MF = n*EF = 7 \times CH_{2}O = C_{(1 \times 7)}H_{(2 \times 7)}O_{(1 \times 7)} = C_{7}H_{14}O_{7}[/tex]                              

Therefore, the molecular formula of CH₂O is C₇H₁₄O₇.

Learn more about molecular formula here:

  • brainly.com/question/1247523
  • brainly.com/question/14327882

I hope it helps you!

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