0.5mols of a mono alkanoicacid weighs 44 grams, determine the molecular formula and name the acid. (show the workings)
mols = grams/molar mass. You have mols and grams, solve for molar mass. I get 88. The COOH group of an alkanoic acid weighs has a molar mass of 45 which leaves88-45 = 43. A methyl group (CH3) is 15 while the methylene group (CH2) is 14 so I would make an educated guess that the compound is CH3CH2CH2COOH to make 88 for the molar mass. Technically, this is a poor question because not all of it can be answered unequivocally. I would name it butanoic acid BUT it could have isomers and that wouldn't bee the correct name.
To determine the molecular formula and name of the mono alkanoic acid, follow these steps:
Step 1: Calculate the molar mass
The molar mass is the mass of one mole of a substance. In this case, we know that 0.5 moles of the acid weighs 44 grams. To calculate the molar mass, divide the mass by the number of moles:
Molar mass = Mass (g) / Moles
Molar mass = 44 g / 0.5 mol
Molar mass = 88 g/mol
Step 2: Determine the empirical formula
The empirical formula represents the simplest whole number ratio of atoms present in a compound. To find the empirical formula, you need additional information about the composition of the acid (or its percentage composition). Without this information, we cannot calculate the empirical formula.
Step 3: Determine the molecular formula
The empirical formula represents the simplest ratio, while the molecular formula tells us the actual number of atoms present in a molecule. To find the molecular formula, we need the molar mass of the compound, which we calculated in Step 1.
Since we have the molar mass (88 g/mol) and assuming it represents the molecular formula, we can determine the ratio of the molecular formula to the empirical formula.
For example, if the empirical formula is CH₂O, and the molar mass is 88 g/mol, we can calculate the ratio:
Molar mass (88 g/mol) / Empirical formula mass (30 g/mol) = 2.93
This indicates that the molecular formula would be approximately three times the empirical formula. Therefore, the molecular formula would be C₃H₆O₃.
Step 4: Name the acid
To name the acid, we use the systematic naming rules for organic acids. Depending on the number of carbon atoms in the alkyl chain, the name will vary.
C₃H₆O₃ is a carboxylic acid with three carbon atoms. The systematic name for this acid is propanoic acid.
So, based on the given information, the molecular formula is C₃H₆O₃, and the name of the acid is propanoic acid.