Q. Water can dissolve more substances than any other liquid because
a) it is dipolar in nature
b) it is a good conductor of heat
c) it has a high value of specific heat
d) it has an oxide of hydrogen
Correct Answer: a) it is dipolar in nature
Question from UPSC Prelims 2021 GS Paper
Explanation :
Why Water is Called the “Universal Solvent”
Water is known as the “universal solvent” because it can dissolve more substances than any other liquid. This unique property is primarily due to the dipolar nature of water molecules.
Water is a polar molecule, meaning it has a partial positive charge on one side and a partial negative charge on the other. This occurs because oxygen is more electronegative than hydrogen, so the shared electrons in the covalent bonds of the water molecule (H2O) spend more time closer to the oxygen atom than to the hydrogen atoms. As a result, the oxygen end of the molecule has a slight negative charge, and the hydrogen ends have a slight positive charge.
This polarity allows water molecules to interact with various ionic and polar substances. When a substance is placed in water, the positive end of the water molecule is attracted to negatively charged ions, and the negative end of the water molecule is attracted to positively charged ions. This interaction helps to separate the ions or molecules from each other and disperse them in the water, effectively dissolving the substance.
Example of Water Dissolving Salt
For example, when table salt (sodium chloride, NaCl) is added to water, the positive part of the water molecules surrounds the negative chloride ions (Cl–), and the negative part of the water molecules surrounds the positive sodium ions (Na+), leading to the dissolution of salt.
Other Properties of Water
The property of water being a good conductor of heat is related to its ability to transfer thermal energy efficiently, but this does not directly contribute to its solvent properties. Water having a high value of specific heat means it can absorb a lot of heat before increasing in temperature, which is important for regulating climate and biological systems, but again, this is not directly related to its ability to dissolve substances. Water being an oxide of hydrogen (H2O) is simply a way to describe its chemical composition and does not explain why it is such a good solvent.