Question

question 21
1 point
your average cup coffee contains 1.15e2 mg of caffeine, how many moles of caffeine are in the cup of coffee? given caffeine is c8h10n4o2 and has a molar mass of 194.0 g/mol.
a 5.93e-1 moles
b 2.23e1 moles
c 5.93e-4 moles
d 2.23e4 moles
e none of the above

Explanation:

Step1: Convert mass to grams

$1.15\text{E}2\ mg = 115\ mg=115\times10^{- 3}\ g = 0.115\ g$

Step2: Use mole - mass formula

The formula for calculating the number of moles $n$ is $n=\frac{m}{M}$, where $m$ is the mass and $M$ is the molar mass. Given $m = 0.115\ g$ and $M=194.0\ g/mol$, then $n=\frac{0.115\ g}{194.0\ g/mol}\approx5.93\times10^{-4}\ mol$

Answer:

C. 5.93E-4 moles