Question

Question 1: How many molecules of C6H14 would you have if you have 5.21 mol? answer has to be within 3 significant figures and in scientific notation.

Question 2 : Consider a 3.21 g sample of C4H10 How many atoms of C would be in this sample? answer with 3 significant figures and in scientific notation.

Thank you

Answer 1

1)

use:

number of molecules = number of mol * Avogadro’s number

number of molecules = 5.21 * 6.022*10^23 molecules

number of molecules = 3.137*10^24 molecules

Answer: 3.14*10^24 molecules

2)

Molar mass of C4H10,

MM = 4*MM(C) + 10*MM(H)

= 4*12.01 + 10*1.008

= 58.12 g/mol

mass(C4H10)= 3.21 g

use:

number of mol of C4H10,

n = mass of C4H10/molar mass of C4H10

=(3.21 g)/(58.12 g/mol)

= 5.523*10^-2 mol

This is number of moles of C4H10

one mole of C4H10 contains 4 mole of C

use:

number of moles of C = 4 * number of moles of C4H10

= 4 * 5.523*10^-2

= 0.2209

use:

number of atoms = number of moles * Avogadro’s number

= 0.2209 * 6.022*10^23 atoms

= 1.33*10^23 atoms

Answer: 1.33*10^23 atoms