Question

lab #11: mole calculations
name
purpose: to become proficient in calculations between mass, moles, molecules and atoms
procedure: for each of the following substances, use the factor label method to calculate the number of moles,
molecules, and atoms. show your work!
data & calculations:
example: calcium chloride - find the mass of a scoop of calcium chloride using a weighing dish.

a) calculate the number of moles in the sample.

b) calculate the number of calcium chloride molecules in the sample.

c) calculate the total number of atoms in the sample.

Explanation:

Step1: Calculate moles

Use the formula \(n=\frac{m}{M}\), where \(n\) is moles, \(m\) is mass, \(M\) is molar mass.
Given \(m = 0.77g\), \(M=110.984g/mol\)
\(n=\frac{0.77g}{110.984g/mol}\approx0.00694mol\)

Step2: Calculate molecules

Use \(N = n\times N_{A}\), \(N_{A}=6.022\times 10^{23}mol^{-1}\)
\(N=0.00694mol\times6.022\times 10^{23}mol^{-1}\approx4.18\times 10^{21}\) molecules

Step3: Calculate atoms

Each \(CaCl_{2}\) molecule has \(3\) atoms (\(1\) Ca and \(2\) Cl).
Total atoms \(=3\times N\)
\(=3\times4.18\times 10^{21}=1.254\times 10^{22}\) atoms

Answer:

a) Approximately \(0.00694mol\)
b) Approximately \(4.18\times 10^{21}\) molecules
c) Approximately \(1.254\times 10^{22}\) atoms