MediumChemistryHigh School (11–12)Organic Compounds with Functional Groups › Haloalkanes and HaloarenesNumerical

A sample of 0.294 g of an aromatic compound has a molar mass of 147 g/mol…

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A sample of $0.294\ \text{g}$ of an aromatic compound has a molar mass of $147\ \text{g/mol}$ . It contains only carbon, hydrogen and chlorine. It is heated with fuming nitric acid and silver nitrate in a sealed tube (the Carius method). All the chlorine is converted into silver chloride, which weighs $0.574\ \text{g}$ after it is dried. Take Cl as $35.5\ \text{g/mol}$ and AgCl as $143.5\ \text{g/mol}$ . Find the mass of chlorine in the sample, the percentage of chlorine, and the number of chlorine atoms in one molecule.

Need a reminder? The key ideaShow

A haloarene is made by ring halogenation, or from a diazonium salt: diazotisation with $\text{NaNO}_2$ and HCl at $273$ to $278\ \text{K}$ , then CuCl or CuBr (Sandmeyer), KI, or $\text{HBF}_4$ and heat. Isomers of a ring are counted by checking which patterns turn into each other by rotating or flipping the ring. Percent yield is $\dfrac{\text{actual}}{\text{theoretical}} \times 100$ .

The worked solution

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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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