Question

Which solvent, water or carbon tetrachloride, would you choose to dissolve each of the following? a. \(\mathrm{KrF}_{2}\) b. \(\mathrm{SF}_{2}\) c. \(\mathrm{SO}_{2}\) d. \(\mathrm{CO}_{2}\) e. \(M g F_{2}\) f. \(C H_{2} O\) g. \(C H_{2}=C H_{2}\)

Short answer

a. Carbon tetrachloride for KrF₂ (nonpolar) b. Water for SF₂ (polar) c. Water for SO₂ (polar) d. Carbon tetrachloride for CO₂ (nonpolar) e. Water for MgF₂ (ionic) f. Water for CH₂O (polar) g. Carbon tetrachloride for CH₂=CH₂ (nonpolar)

Step-by-step solution

a. KrF₂

KrF₂ is a nonpolar substance. Nonpolar substances dissolve better in nonpolar solvents. Therefore, it is better to use carbon tetrachloride to dissolve KrF₂.

b. SF₂

SF₂ is a polar substance. Polar substances dissolve better in polar solvents. Therefore, it is better to use water to dissolve SF₂.

c. SO₂

SO₂ is a polar substance. Polar substances dissolve better in polar solvents. Therefore, it is better to use water to dissolve SO₂.

d. CO₂

CO₂ is a nonpolar substance. Nonpolar substances dissolve better in nonpolar solvents. Therefore, it is better to use carbon tetrachloride to dissolve CO₂.

e. MgF₂

MgF₂ is an ionic compound, which means it contains positively and negatively charged ions. Ionic compounds dissolve better in polar solvents. Therefore, it is better to use water to dissolve MgF₂.

f. CH₂O

CH₂O has a bent molecular geometry, which makes it polar. Polar substances dissolve better in polar solvents. Therefore, it is better to use water to dissolve CH₂O.

g. CH₂=CH₂

CH₂=CH₂ is a nonpolar substance due to its linear molecular geometry and equal sharing of electrons between carbon atoms. Nonpolar substances dissolve better in nonpolar solvents. Therefore, it is better to use carbon tetrachloride to dissolve CH₂=CH₂.

Key concepts

Polar vs Nonpolar Solvents

Understanding the difference between polar and nonpolar solvents is crucial in chemistry. Solvents are substances, usually liquids, that dissolve solutes to form a solution.
Polar solvents, like water, have molecules with a partial electrical charge. This happens because one end of the molecule has slightly negative charges, while the other end has slightly positive charges. This charge separation due to differences in electronegativity makes them effective at dissolving other polar substances or ionic compounds.
Nonpolar solvents, such as carbon tetrachloride, have molecules where the electrons are shared equally, resulting in no charge separation. These solvents are best for dissolving nonpolar substances, where the electron sharing is equal, leading to no charged ends.
In summary:

• Polar solvents dissolve polar solutes or ionic compounds.
• Nonpolar solvents dissolve nonpolar solutes.

Matching solvents with the right type of solute is vital for successful solubility.

Molecular Polarity

Molecular polarity dictates how substances interact with solvents. It is determined by the shape and charge distribution of molecules.
If a molecule has an uneven distribution of electrons and a distinct positive and negative end, it is polar. This often results from differences in electronegativity between atoms in a molecule and the asymmetrical arrangement of these atoms. For example, \( ext{SO}_{2}\) has a bent shape and a polar nature because of the significant electronegativity difference between sulfur and oxygen.
On the other hand, nonpolar molecules have a balanced charge distribution, with electrons shared equally among atoms. Consider \( ext{CO}_{2}\): although carbon and oxygen have different electronegativities, the linear molecule's symmetry results in an overall nonpolar nature.
Key points to remember:

• Polar molecules have an uneven charge distribution.
• Nonpolar molecules have a balanced electron distribution.

The polarity influences how molecules interact with different solvents, following the rule that 'like dissolves like.'

Ionic Compounds and Solvents

Ionic compounds consist of positively and negatively charged ions. They don't share electrons evenly; instead, ions are held together by electrostatic forces. This structure heavily influences their solubility.
Polar solvents like water are excellent for dissolving ionic compounds because the positive end of the polar water molecules attracts negatively charged ions, while the negative end attracts positively charged ions. This solvent interaction with ions helps break ionic bonds, enabling dissolution.
Examples include \( ext{MgF}_{2}\), where magnesium ions are positively charged, and fluoride ions are negatively charged. In water, these ions become surrounded by water molecules, which separate and stabilize them in solution.
Important aspects:

• Ionic compounds dissolve in polar solvents.
• Water is a common polar solvent for ionic substances.

Understanding these interactions is crucial for predicting solubility behaviors in various chemical scenarios.