Question
1. Answer the following questions about water. (a) Draw the Lewis diagram for water. (b) Is water polar or nonpolar? Explain. (c) What kind(s) of intermolecular forces exist in a sample of pure water? 2. If water is the "universal solvent," why do you need to add detergent when washing clothes?
Answer
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Vesper
Master · Tutor for 5 years
Answer
1.(a) The Lewis diagram of water shows an oxygen atom in the center with two hydrogen atoms bonded to it and two lone pairs of electrons on the oxygen.(b) Water is polar.(c) Hydrogen bonds are the dominant intermolecular forces in pure water.2. Detergents are needed when washing clothes to emulsify nonpolar substances like oils and grease, enabling them to be rinsed away by water.
Explanation
1. (a) The Lewis diagram of water (H₂O) involves two hydrogen atoms forming single bonds with an oxygen atom. The oxygen has two lone pairs of electrons. (b) Water (H₂O) is polar. This is because the oxygen atom is more electronegative than the hydrogen atoms, creating a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms. The bent shape of the molecule adds to the asymmetry, leading to a dipole moment.(c) In a sample of pure water, the primary intermolecular forces are hydrogen bonds. These occur because the hydrogen atoms are bonded to the highly electronegative oxygen atoms, allowing hydrogen bonds to form between the hydrogen of one molecule and the oxygen of another.2. Water is termed the "universal solvent" due to its ability to dissolve a wide range of substances, particularly polar substances and ionic compounds. However, it is not effective at dissolving nonpolar substances, like oils and grease, commonly found on clothes. Detergents contain surfactants that have both hydrophobic (nonpolar) and hydrophilic (polar) properties. The hydrophobic part binds to nonpolar substances (such as oils and grease), while the hydrophilic part interacts with water, allowing the nonpolar substances to be emulsified and washed away.