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3 years ago

Which is untrue about covalent compounds?

Chemistry

2 answers:

Elodia [21]3 years ago

7 0

Answer: Have high melting point.

Explanation:

Covalent compounds are known to have low melting point because they have weak forces of attraction between the binding molecules, so low amount of energy is needed to break the binding force.

scoundrel [369]3 years ago

3 0

The untrue statement is that they high melting points.

The covalent compounds are the compounds exhibiting strong intra-molecular bonds. This is due to the tightness of the atoms within the covalent molecules. The force of attraction between the individual molecules in a covalent compound seems to be weak. The covalent compounds exhibit weak intermolecular forces that hold the atoms together due to this they have a low melting point.

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If a buffer contains 1.05M B and 0.750M BH+ has the pH of 9.5. What would be the pH after 0.005mol of HCL is added to 0.5L of so

Leviafan [203]

Answer:

Final pH: 9.49.

Round to two decimal places as in the question: 9.5.

Explanation:

The conjugate of B is a cation that contains one more proton than B. The conjugate of B is an acid. As a result, B is a weak base.

What's the pKb of base B?

Consider the Henderson-Hasselbalch equation for buffers of a weak base and its conjugate acid ion.

$\displaystyle \text{pOH} = \text{pK}_b + \log{\frac{[\text{Salt}]}{[\text{Base}]}}$ .

$\text{pOH} = \text{pK}_w - \text{pH}$ .

$\text{pK}_w = 14$ .

$\text{pOH} = 14 - 9.5 = 4.5$

$\displaystyle \text{pK}_b = \text{pOH} -\log{\frac{[\text{Salt}]}{[\text{Base}]}}\\\phantom{\text{pK}_b} = 4.5 - \log{\frac{0.750}{1.05}} \\\phantom{\text{pK}_b} =4.64613$ .

What's the new salt-to-base ratio?

The 0.005 mol of HCl will convert 0.005 mol of base B to its conjugate acid ion BH⁺.

Initial:

$n(\text{B}) = c\cdot V = 1.05 \times 0.5 = 0.525\;\text{mol}$ ;
$n(\text{BH}^{+}) = c\cdot V = 0.750 \times 0.5 = 0.375\;\text{mol}$ .

After adding the HCl:

$n(\text{B}) = 0.525 - 0.005 = 0.520\;\text{mol}$ ;
$n(\text{BH}^{+}) = 0.375+ 0.005 = 0.380\;\text{mol}$ .

Assume that the volume is still 0.5 L:

$\displaystyle [\text{B}] = \frac{n}{V} = \frac{0.520}{0.5} = 1.04\;\text{mol}\cdot\text{dm}^{-3}$ .
$\displaystyle [\text{BH}^{+}] = \frac{n}{V} = \frac{0.380}{0.5} = 0.760\;\text{mol}\cdot\text{dm}^{-3}$ .

What's will be the pH of the solution?

Apply the Henderson-Hasselbalch equation again:

$\displaystyle \text{pOH} = \text{pK}_b + \log{\frac{[\text{Salt}]}{[\text{Base}]}} = 4.64613 + \log{\frac{0.760}{1.04}} = 4.50991$

$\text{pH} = \text{pK}_w - \text{pOH}= 14 - 4.50991 = 9.49$ .

The final pH is slightly smaller than the initial pH. That's expected due to the hydrochloric acid. However, the change is small due to the nature of buffer solutions: adding a small amount of acid or base won't significantly impact the pH of the solution.

3 0

3 years ago

Which is the reason that ionic compounds are brittle?

lisabon 2012 [21]

Ionic bonds are the weakest bonds.

7 0

3 years ago

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Select the correct answer. What is the number of protons in this carbon atom? A. 12 B. 6 C. 18 D. 24

andrew11 [14]

Answer:

The correct answer is

C. 6 Protons

Explanation:

Carbon is a nonmetallic element that is available in both organic and inorganic compounds.

Carbon belongs to group 14 elements in the periodic table,carbon is a chemical element with the symbol C and atomic number 6, it can form long chains with its own atoms, a feature called catenation.

Two allotropes of carbon available are diamonds and graphites, which have different crystalline structures

The physical properties of carbon vary widely with the allotropic form.

examples are.

Graphite, diamonds and coal are all nearly pure forms of carbon
Diamond is highly transparent. Graphite is opaque and black
Diamond is one of the hardest substances known to man. Graphite is soft and often used as the "lead" in lead pencils
Diamond has a very low electrical conductivity. Graphite is a very good conductor
Very brittle, and cannot be rolled into wires or pounded into sheets

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3 years ago

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ra1l [238]

Answer:

b. . the element symbol

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Which scientist discovered that other galaxies and stars were moving away from us at speeds proportional to how far they were aw

julsineya [31]

I think it was edwin hubble but I'm not sure

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