Question 4.6: Molecular Weight What is the molecular weight of (a) glucose...

Introduction to General, Organic, and Biochemistry

Molecular Weight
What is the molecular weight of (a) glucose, $\text{C}_{6}\text{H}_{12}\text{O}_{6}$ , and (b) urea, ${(\text{NH}_{2})_{2}}\text{CO}$ ?

Strategy
Molecular weight is the sum of the atomic weights of all atoms in the molecular formula expressed in atomic mass units (amu).

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\text{(a) Glucose}, \text{C}_{6}\text{H}_{12}\text{O}_{6}\hspace{30 pt} \hspace{15 pt} \text{(b) Urea}, {(\text{NH}_{2})_{2}}\text{CO}\\ \hspace{15 pt} \text{C} \quad 6\times 12.0 = 72.0 \hspace{50 pt} \text{N} \quad 2 \times 14.0 = 28.0 \\ \hspace{15 pt} \text{H} \quad 12\times 1.0 = 12.0 \hspace{50 pt} \text{H} \quad 4\times 1.0 = 4.0 \\ \hspace{15 pt} \underline{\text{O} \quad 6\times 16.0 = 96.0} \hspace{50 pt} \text{C} \quad 1\times 12.0 = 12.0 \\ \hspace{29 pt} \text{C}_{6}\text{H}_{12}\text{O}_{6} = 180.0 \, \text{amu}  \hspace{23 pt} \underline{\text{O} \quad 1\times 16.0 = 16.0} \\ \hspace{15 pt} \hspace{140 pt} {(\text{NH}_{2})_{2}}\text{CO} = 60.0  \, \text{amu}

■ Quick Check 4.6
What is (a) the molecular weight of ibuprofen, $\text{C}_{13}\text{H}_{18}\text{O}_{2}$ , and (b) the formula weight of barium phosphate, $\text{Ba}_{3}{(\text{PO}_{4})_{2}}$ ?

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