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3 years ago

12. Compare and contrast hydrogen bonds and van der Waals interactions.

Chemistry

1 answer:

mrs_skeptik [129]3 years ago

4 0

Explanation:

Van der Waals interactions occur between any two or more molecules. They are caused by a fluctuation in electron density, as electrons are not actually fixed in a shell, but actually freely moving as a 'cloud of electron density'. This means that sometimes one end of a molecule can become more partially negatively charged as all electrons move to that side, and conversely it can attract the more partially positive end of a molecule (that has little electrons).

Hydrogen bonds only occur between molecules that contain oxygen, nitrogen and fluorine bonded to a hydrogen atom.

Hydrogen bonding is also the strongest intermolecular force there is, but not strong in comparison to ionic and covalent bonds. Therefore, hydrogen bonds are much stronger than Van der Waals forces. Hydrogen bonds only form if oxygen, nitrogen and fluorine are bonded to a hydrogen atom, as they have the greatest electronegativity differences (look at an electronegativity table), and when the overall molecule is polar (have unequal charges). This allows the molecule to be able to attract another molecule from one of the bonded atoms to a hydrogen atom.

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Assuming that an acetic acid solution is 12% by mass and that the density of the solution is 1.00 g/mL, what volume of 1 M NaOH

Doss [256]

Explanation:

Let us assume that total mass of the solution is 100 g. And, as it is given that acetic acid solution is 12% by mass which means that mass of acetic acid is 12 g and 88 g is the water.

Now, calculate the number of moles of acetic acid as its molar mass is 60 g/mol.

No. of moles = $\frac{mass}{\text{molar mass}}$

= $\frac{12 g}{60 g/mol}$

= 0.2 mol

Molarity of acetic acid is calculated as follows.

Density = $\frac{mass}{volume}$

1 g/ml = $\frac{100 g}{volume}$

volume = 100 ml

Hence, molarity = $\frac{\text{no. of moles}}{volume}$

= $\frac{0.2 mol}{0.1 L}$

= 2 mol/l

As reaction equation for the given reaction is as follows.

$NaOH + CH_{3}COOH \rightarrow CH_{3}COONa + H_{2}O$

So, moles of NaOH = moles of acetic acid

Let us suppose that moles of NaOH are "x".

$x \times 1 M = 10 mL \times 2 M$ (as 1 L = 1000 ml)

x = 20 L

Thus, we can conclude that volume of NaOH required is 20 ml.

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Answer:

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