Question

How many C atoms are present in a 7.37 ng sample of quinine, C20H24O2N2? Note: 1 ng is one nanogram. Enter your answer in exponential notation, e.g. 1.23e20 for 1.23x1020. Do not include any units or words as part of your answer. Give your answer accurate to three significant figures. Molar masses (in g mol−1): H, 1.008 C, 12.01 N, 14.01 O, 16.00

Answer 1

There are approximately 1.926 x 10^14 C atoms in the given sample of quinine.

Step-by-step explanation:

To find the number of carbon (C) atoms in a sample of quinine, we need to consider the molar mass of quinine and the amount of the sample given.

First, we calculate the molar mass of quinine by summing the atomic masses of each element in the formula:

C20H24O2N2

(20 x 12.01 g/mol) + (24 x 1.008 g/mol) + (2 x 16.00 g/mol) + (2 x 14.01 g/mol) = 324.41 g/mol

Next, we convert the given sample mass from nanograms (ng) to grams (g) using the conversion factor:

7.37 ng x (1 g / 1e9 ng) = 7.37e-9 g

To find the number of moles of quinine in the sample, we use the equation:

moles = mass / molar mass

moles = 7.37e-9 g / 324.41 g/mol

Now, we can calculate the number of C atoms in the sample by multiplying the number of moles of quinine by Avogadro's number (6.022 x 10^23 C atoms/mol):

C atoms = moles x (6.022 x 10^23 C atoms/mol)

C atoms = (7.37e-9 g / 324.41 g/mol) x (6.022 x 10^23 C atoms/mol)

Performing the calculations:

C atoms = 1.926e14 C atoms

Therefore, there are approximately 1.926 x 10^14 C atoms in the given sample of quinine.