Question

An average cup of coffee contains about 125 mg of caffeine, C8H10N4O2. How many moles of caffeine are in a cup, and how many molecules of caffeine?

Answer 1

Answer:

Explanation:

moles=mass/molar mass

          = 125*10*-3/C8H10N4O2

           =125*10*-3/12*8+10*1+14*4+16*2

           = 125*10*-3/194

           = 6.44*10*-4 moles

molecules= moles*Avogadro's number

                = 6.44*10*-4*6.022*10*23

                =3.8*10*20 molecules

Tried my best to explain this:

• moles formed are 6.44 multiplied by 10 to the power minus 4.

• molecules formed are 3.8 multiplied by 10 to the power 20.
• Multipled 10 raised to power minus 3 in the start because milli is 10*-3.