Problem 50 - Chemistry: The Central Science

Question

Determine the molecular and empirical formulas of the following: (a) the organic solvent benzene, which has six carbon atoms and six hydrogen atoms; (b) the compound silicon tetrachloride, which has a silicon atom and four chlorine atoms and is used in the manufacture of computer chips; (c) the reactive substance diborane, which has two boron atoms and six hydrogen atoms; (d) the sugar called glucose, which has six carbon atoms, twelve hydrogen atoms, and six oxygen atoms.

Step-by-Step Solution

Answer

The molecular and empirical formulas of the given substances are as follows: (a) Benzene has a molecular and empirical formula of C6H6. (b) Silicon tetrachloride has a molecular and empirical formula of SiCl4. (c) Diborane has a molecular formula of B2H6 and an empirical formula of BH3. (d) Glucose has a molecular formula of C6H12O6 and an empirical formula of CH2O.

Step 1: (a) Benzene

Molecular formula: Benzene has six carbon atoms and six hydrogen atoms, so its molecular formula is C6H6. Since the ratio of the carbon atoms to the hydrogen atoms is 1:1 and there are no more common factors, the empirical formula is also C6H6.

Step 2: (b) Silicon Tetrachloride

Molecular formula: Silicon tetrachloride has one silicon atom and four chlorine atoms, so its molecular formula is SiCl4. The ratio of silicon atoms to chlorine atoms is 1:4, which is already the simplest whole number ratio. Therefore, the empirical formula is also SiCl4.

Step 3: (c) Diborane

Molecular formula: Diborane has two boron atoms and six hydrogen atoms, so its molecular formula is B2H6. To find the empirical formula, we need to find the simplest whole number ratio between boron and hydrogen atoms. The ratio is 2:6, which can be simplified to 1:3 by dividing both sides by 2. Therefore, the empirical formula for diborane is BH3.

Step 4: (d) Glucose

Molecular formula: Glucose has six carbon atoms, twelve hydrogen atoms, and six oxygen atoms, so its molecular formula is C6H12O6. To find the empirical formula, we must find the simplest whole number ratio for carbon, hydrogen, and oxygen atoms. The ratio is 6:12:6, and we can divide each by 6 to get the simplest whole number ratio of 1:2:1. Therefore, the empirical formula for glucose is CH2O.