1. Which of the following is least soluble in water?
QUESTION:
Which of the following is least soluble in water?
A. NH3, B. HF, C. CH4,
Solubility in water depends on the ability of molecules to attract water molecules. In general, more polar molecules are more soluble in water. The is the “Like dissolves like” rule; water is polar.
Which of the following is least soluble in water?
A. NH3, B. HF, C. CH4,
PAUSE CLICK Solubility in water depends on the ability of molecules to attract water molecules. In general, more polar molecules are more soluble in water.
The is the “Like dissolves like” rule. Water is polar, and polar substances tend to be more soluble in water than nonpolar substances.
This question is asking for the least soluble substance. So we need to look for the substance made up of nonpolar molecules.
By now, you should be able to figure out that methane (CH4) is nonpolar.
Therefore the correct answer is C.
HF and NH3 are both polar molecules. Moreover, these molecules are also capable of hydrogen bonding interactions with water molecules.
Here’s a model of the ammonia molecule.
THe hydrogen atoms are bonded to nitrogen, which is highly electgronegative.
Therefore, the hydrogen atoms, such as this one
HIGHLIGHT bottom H
would be very attractive to a lone pair of the oxygen atom of a nearby water molecule.
CLICK
THe nitrogen atom in ammonia also has a lone pair. It would be strongly attracted
to a hydrogen atom of a nearby water molecule.
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2. Video ID: © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08