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Chapter 3: Problem 38

Adenine, a component of nucleic acids, has the mass percent composition: \(44.45 \%\) C \(, 3.73 \%\) H, \(51.82 \%\) N. Its molecular mass is 135.14 u. What is its molecular formula?

Short Answer

Expert verified
The molecular formula of Adenine is \(CHN\)

Step by step solution

01

Convert mass percent into grams and find moles

First, convert the mass percentage into grams. Assume that the total mass is 100 g, thus there are \(44.45 g\) of Carbon, \(3.73 g\) of Hydrogen, and \(51.82 g\) of Nitrogen. Then, divide each mass by the atomic mass to find the number of moles: \(C: \frac{44.45 g}{12.01 g/mol} = 3.70 mol\) , \(H: \frac{3.73 g}{1.01 g/mol} = 3.69 mol\), \(N: \frac{51.82 g}{14.01 g/mol} = 3.70 mol\)
02

Find element ratio

Find the ratio of each element to the smallest number of moles. In this case, the smallest number of moles is \(3.69 mol\) (Hydrogen). So the ratio of C, H, and N to H are as follows: \(C: \frac{3.70 mol}{3.69 mol} \approx 1\), \(H: \frac{3.69 mol}{3.69 mol} = 1\), \(N: \frac{3.70 mol}{3.69 mol} \approx 1\)
03

Convert to whole numbers

Since the ratios found are all approximate to 1 and are very close to whole numbers, there is no need for a multiplier. However, if the ratio is a fraction, a suitable multiplier (2, 3, etc.) should be used to convert the ratio into whole numbers.
04

Write the molecular formula

Combine the results from the previous steps to write the molecular formula. Use the symbols of the elements (C for Carbon, H for Hydrogen, and N for Nitrogen), followed by the subscript of the number ratio which in this case is all 1. The molecular formula is therefore \(C_1H_1N_1\) or simply \(CHN\)

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Most popular questions from this chapter

The food flavor enhancer monosodium glutamate (MSG) has the composition \(13.6 \%\) Na, \(35.5 \%\) C. \(4.8 \% \mathrm{H}, 8.3 \% \mathrm{N}, 37.8 \% \mathrm{O},\) by mass. What is the empirical formula of MSG?

Nitrogen forms five oxides in which its oxidation states are \(+1,+2,+3,+4,\) and \(+5,\) respectively. Write appropriate formulas for these compounds.

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