Question

Neurotransmitters are important chemicals in the brain that assist in the firing of neurons. Norephinephrine is a neurotransmitter that is released in the body when the body is threatened or depressed. It contains 56.8 percent carbon, 6.5 percent hydrogen, 28.4 percent oxygen, and 8.3 percent nitrogen. It has a molar mass of 169 g/mole. What is its molecular formula?​

Answer 1

To find the molecular formula of norepinephrine, we need to determine the number of atoms of each element present in the molecule. We can do this by dividing the percent composition of each element by its atomic mass and rounding to the nearest whole number.

For carbon, the number of atoms present is 56.8% / 12 g/mol = 4.73 atoms. Rounding to the nearest whole number gives us 5 atoms.

For hydrogen, the number of atoms present is 6.5% / 1 g/mol = 6.5 atoms. Rounding to the nearest whole number gives us 7 atoms.

For oxygen, the number of atoms present is 28.4% / 16 g/mol = 1.78 atoms. Rounding to the nearest whole number gives us 2 atoms.

For nitrogen, the number of atoms present is 8.3% / 14 g/mol = 0.59 atoms. Rounding to the nearest whole number gives us 1 atom.

The molecular formula of norepinephrine is therefore C5H7NO.