Chapter F Problem 15

[Anish Patel 4B]

Diazepam, a drug used to treat anxiety, has the mass percentage composition 67.49% C, 4.60% H, 12.45% Cl, 9.84% N, and 5.62% O. What is the empirical formula of the compound?

I was wondering how we would calculate the molar mass of diazepam to solve for its empirical formula? Is this a common compound we should know?

[JChen_2I]

You would solve for a sample of 100g therefore you'd have 67.49g of carbon, 4.60g of hydrogen, 12.45g of chlorine, 9.84g of nitrogen, and 5.62 g of oxygen. Convert these masses to moles using their molar mass and then divide by the smallest molar value which is chlorine with 0.3512 mol. Divide the moles of each element by 0.3512 and you'll get a ratio of C16H13ClN2O

[Aadil Rehan 1D]

You don't need molar mass to calculate the empirical, only the molecular. Assume a 100g sample to find empirical.

[TYun_1C]

Just assume that the sample is 100 grams and turn all the percents into grams. From there you can convert the grams of elements into moles then divide all the moles by the smallest number of moles. This will give you a relative ratio of each element within the compound. Since the empirical formula is the lowest whole number ratio, keep multiplying until the numbers all become whole and these will be the subscripts for each element in diazepam. As for if it is a compound we should know, I guessing not but it always wouldn't hurt to know it!

[Nick Lewis 4F]

Diazepam, a drug used to treat anxiety, has the mass percentage composition 67.49% C, 4.60% H, 12.45% Cl, 9.84% N, and 5.62% O. What is the empirical formula of the compound?

I was wondering how we would calculate the molar mass of diazepam to solve for its empirical formula? Is this a common compound we should know?

You do not need to know the molar mass of diazepam to get the empirical formula. If you are given a molar mass of this compound, then usually they are asking you to find the molecular formula, where you compare the molar mass of the given compound with the molar mass of your empirical formula. It's usually a pretty clean ratio and not hard to get from empirical to molecular formula.