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3 years ago

Why is CN considered a weak base if its the conjugate base of a weak acid?

1 answer:

8 0

CN considered as a weak base even if its the conjugate base of a weak acid. When it is in aqueous solution, it accepts a hydrogen ion forming hydrogen cynide and an OH- ions which makes it a Bronsted -Lowry base. Also, it has a pKb of 4.79 which makes it basic in nature.

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Muscle physiologists study the accumulation of lactic acid [ch3ch(oh)cooh] during exercise. food chemists study its occurrence i

Drupady [299]

The provided information are:
volume of 0.85 M lactic acid = 225 ml
volume of 0.68 M sodium lactate = 435 ml
Ka of the lactate buffer = 1.38 x 10⁻⁴
The equation for dissociation of lactic acid is:
CH₃CH(OH)COOH(aq) + H₂O ⇄ CH₃CH(OH)COO⁻(aq) + H₃O⁺(aq)
The pH of buffer is calculated from Henderson-Hasselbalch equation, which is:
pH = pKa + log $\frac{[conjugated base]}{[Acid]}$
pKa = - log Ka = - log (1.38 x 10⁻⁴) = 3.86
The number of moles of lactic acid and lactate are as follows:
n (Lactic acid) = 225 ml x 0.85 mmol/ml = 191.25 mmol
n (Lactate) = 435 ml x 0.68 mmol/ml = 295.8 mmol
The number of moles of lactic acid and lactate in total volume of the solution:
[CH₃CH(OH)COOH] = n (lactic acid) / 660 ml = 191.25 mmol / 660 ml = 0.29 M
[CH₃CH(OH)COO⁻] = n (lactate) / 660 ml = 0.45 M
pH = 3.86 + log $\frac{0.45 M}{0.29 M}$ = 3.86 + 0.191 = 4.05
So the pH of given solution is 4.05

7 0

3 years ago

How many atoms in chemical formula NaCl

musickatia [10]

Answer:

2 atoms

Explanation:

1 sodium atom + 1 chlorine atom = 2 atoms

4 0

3 years ago

A sample of carbon dioxide occupies a 5.13 dm3 container at STP. What is the volume of the gas at a pressure of 286.5 kPa and a

suter [353]

Considering the ideal gas law and STP conditions, the volume of the gas at a pressure of 286.5 kPa and a temperature of 12.9°C is 1.8987 L.

<h3>Definition of STP condition</h3>

The STP conditions refer to the standard temperature and pressure. Pressure values at 1 atmosphere and temperature at 0 ° C are used and are reference values for gases. And in these conditions 1 mole of any gas occupies an approximate volume of 22.4 liters.

<h3>Ideal gas law</h3>

Ideal gases are a simplification of real gases that is done to study them more easily. It is considered to be formed by point particles, do not interact with each other and move randomly. It is also considered that the molecules of an ideal gas, in themselves, do not occupy any volume.

The pressure, P, the temperature, T, and the volume, V, of an ideal gas, are related by a simple formula called the ideal gas law:

P×V = n×R×T

where:

P is the gas pressure.
V is the volume that occupies.
T is its temperature.
R is the ideal gas constant. The universal constant of ideal gases R has the same value for all gaseous substances.
n is the number of moles of the gas.

<h3>Volume of gas</h3>

In first place, you can apply the following rule of three: if by definition of STP conditions 22.4 L are occupied by 1 mole of carbon dioxide, 5.13 L (5.13 dm³= 5.13 L, being 1 dm³= 1 L) are occupied by how many moles of carbon dioxide?

$amount of moles of carbon dioxide=\frac{5.13 Lx1 mole of carbon dioxide}{22.4 L}$

<u><em>amount of moles of carbon dioxide= 0.229 moles</em></u>

Then, you know:

P= 286.5 kPa= 2.8275352 atm (being 1 kPa= 0.00986923 atm)
V= ?
T= 12.9 C= 285.9 K (being 0°C= 273 K)
R= 0.082 $\frac{atmL}{mol K}$
n= 0.229 moles

Replacing in the ideal gas law:

2.8275352 atm× V = 0.229 moles×0.082 $\frac{atmL}{mol K}$ × 285.9 K

Solving:

V= (0.229 moles×0.082 $\frac{atmL}{mol K}$ × 285.9 K)÷ 2.8275352 atm

Finally, the volume of the gas at a pressure of 286.5 kPa and a temperature of 12.9°C is 1.8987 L.

Learn more about

STP conditions:

brainly.com/question/26364483

brainly.com/question/8846039

brainly.com/question/1186356

the ideal gas law:

brainly.com/question/4147359

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5 0

2 years ago

Urea, (NH2)2CO, is a product of metabolism of proteins. An aqueous solution is 37.2% urea by mass and has a density of 1.032 g/m

Feliz [49]

Answer:

The molarity of urea in this solution is 6.39 M.

Explanation:

Molarity (M) is <em>the number of moles of solute in 1 L of solution</em>; that is

$molarity = moles of solute ÷ liters of solution$

To calculate the molality, we need to know the number of moles of urea and the volume of solution in liters. We assume 100 grams of solution.

Our first step is to calculate the moles of urea in 100 grams of the solution,

using the molar mass a conversion factor. The total moles of 100g of a 37.2 percent by mass solution is

60.06 g/mol ÷ 37.2 g = 0.619 mol

Now we need to calculate the volume of 100 grams of solution, and we use density as a conversion factor.

1.032 g/mL ÷ 100 g = 96.9 mL

This solution contains 0.619 moles of urea in 96.9 mL of solution. To express it in molarity, we need to calculate the moles present in 1000 mL (1 L) of the solution.

0.619 mol/96.9 mL × 1000 mL= 6.39 M

Therefore, the molarity of the solution is 6.39 M.

4 0

3 years ago

Which is a limitation of comparative investigations?

IgorC [24]

Answer:

hi............

Explanation:

7 0

3 years ago

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