Select the correct answer.
What is the mass percent of chlorine in chloroform $\left( CHCl _3\right)$ ?
(The molar mass of $C =1201 H =1.0079$, and $Cl =35.45$.)
A. $10.061 \%$
B. $29.698 \%$
C. $59.396 \%$
D. $89.094 \%$
E. $98.298 \%$
Answer (1)
Calculate the molar mass of chloroform ( C H C l 3 ): 12.01 + 1.0079 + 3 ( 35.45 ) = 119.3679 g/mol.
Calculate the mass of chlorine in chloroform: 3 ( 35.45 ) = 106.35 g/mol.
Determine the mass percent of chlorine in chloroform: 119.3679 106.35 × 100 .
The mass percent of chlorine in chloroform is 89.094% .
Explanation
Problem Analysis We are asked to calculate the mass percent of chlorine in chloroform ( C H C l 3 ). We are given the molar masses of carbon ( C = 12.01 g/mol), hydrogen ( H = 1.0079 g/mol), and chlorine ( Cl = 35.45 g/mol).
Molar Mass Calculation First, we need to calculate the molar mass of chloroform ( C H C l 3 ). This is done by summing the molar masses of each element in the compound, multiplied by the number of atoms of that element in the compound.
Molar mass of C H C l 3 = ( 1 × C ) + ( 1 × H ) + ( 3 × Cl )
Calculating Molar Mass of Chloroform Substituting the given molar masses, we get:
Molar mass of C H C l 3 = ( 1 × 12.01 ) + ( 1 × 1.0079 ) + ( 3 × 35.45 )
Molar mass of C H C l 3 = 12.01 + 1.0079 + 106.35
Molar mass of C H C l 3 = 119.3679 g/mol
Calculating Mass of Chlorine Next, we calculate the mass of chlorine in one mole of chloroform. Since there are three chlorine atoms in one molecule of chloroform, the mass of chlorine is:
Mass of chlorine = 3 × 35.45 = 106.35 g/mol
Calculating Mass Percent of Chlorine Now, we can calculate the mass percent of chlorine in chloroform using the formula:
Mass percent of chlorine = Molar mass of C H C l 3 Mass of chlorine × 100
Mass percent of chlorine = 119.3679 106.35 × 100
Mass percent of chlorine = 0.890943 × 100
Mass percent of chlorine = 89.0943%
Final Answer Therefore, the mass percent of chlorine in chloroform is approximately 89.094% .
Examples
Understanding mass percent is crucial in various fields. For instance, in environmental science, it helps determine the concentration of pollutants in a sample. In pharmaceuticals, it ensures the correct dosage of active ingredients in a medication. Knowing the mass percent allows for accurate and safe use of chemical compounds in everyday applications.
