Question

A crime lab received a 235-gram sample. The sample had a molecular mass of 128.1 grams and the empirical formula is CH2O. How many grams of each element are in the sample?

Answer 1

Explanation:

Given parameters:

Mass of sample = 235g

Molecular mass of sample = 128.1g

Empirical formula = CH₂O

Unknown:

Mass of each element in the sample = ?

Solution:

To solve this problem, we must know that the empirical formula of any compound is the simplest ratio of the atoms it contains. This is not the true formula of the compound.

      Molecular formula = (Empirical formula)ₙ

Let us find the molecular mass of the sample;

      CH₂O = 12 + 2(1) + 16 = 30g

   

      128.1  = (30)n

          n = 4

The molecular formula of the compound is;    (CH₂O)₄  = C₄H₈O₄

Now to find the grams of each element in the sample;

Express the molecular mass of each element and that of the compound as a fraction and multiply with the given mass;

    For C;

              $\frac{4 x 12}{128.1} x 235$  = 88.06g

          H; $\frac{8 x 1}{128.1} x 235$  = 14.68g

          O: $\frac{4 x 16}{128.1} x 235$ = 117.41g

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Mass composition brainly.com/question/3018544

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