Determine the number of protons, electron and neutrons present in an atom of magnesium

What amounts of sodium benzoate would be required to prepare 2.5L of 0.35M benzoic buffer solution with a pH of 6.10? Ka of benz

slava [35]

Answer:

Benzoic acid: 1.288g

Sodium benzoate: 124.48g

Explanation:

Benzoic acid, HC7H5O2 is in equilibrium with its conjugate base, C7H5O2⁻ producing a buffer. The pH of the buffer can be determined following H-H equation:

pH = pKa + log [C7H5O2⁻] / [HC7H5O2] (1)

<em>Where pH is desire pH = 6.10 pKa is -log Ka = 4.187 and [] are molar concentrations of the buffer.</em>

As you want to prepare 2.5L of a 0.35M of buffer, moles of buffer are:

2.5L ₓ (0.35mol / L) = 0.875moles of buffer.

And you can write:

0.875 moles = [C7H5O2⁻] + [HC7H5O2] (2)

Replacing (2) in (1)

pH = pKa + log [C7H5O2⁻] / [HC7H5O2]

6.10 = 4.187 + log [C7H5O2⁻] / [HC7H5O2]

1.913 = log [C7H5O2⁻] / [HC7H5O2]

81.846 = 0.875mol - [HC7H5O2] / [HC7H5O2]

81.846 [HC7H5O2] = 0.875mol - [HC7H5O2]

82.846 [HC7H5O2] = 0.875mol

<h3>[HC7H5O2] = 0.01056 moles</h3>

And moles of the benzoate, [C7H5O2⁻]:

[C7H5O2⁻] = 0.875mol - 0.01056mol =

Using molar mass of benzoic acid and sodium benzoate, amount of each compound you must add to prepare 2.5L of the buffer are:

Benzoic acid: 0.01056mol ₓ (122.01g/mol) = 1.288g

Sodium benzoate: 0.8644mol ₓ (144.01g/mol) = 124.482g

3 0

3 years ago

Problem: In each of the following situations, what type of filtration device would you use?

Shtirlitz [24]

Answer:

A. Filtration by gravity

B. Syringe filter

C. Syringe filter

D. Filtration by gravity

E. Syringe filter

F. Filtration by gravity / Vacuum filtration.

Explanation:

Filtration is a mixture of separation techniques to separate solids from liquids. The filtration can be done by gravity, by pressure or by vacuum. The correct filtration is chosen by the characteristics of the mixture.

A. The particles are big, so it's possible to use a funnel and a filter paper with the right numeration (the diameter of the pores must be smaller than the particles). The filtration will happen by gravitation.

B. Because the volume is too small (1 mL), it can be used as a syringe filter, a small device in which the solution is put in the syringe, and then, by pressure, the solution goes from the filter. Thus, the filtration is done by pressure.

C. As letter B, the small volume indicates a pressure filtration by a syringe filter.

D. In this case, such as letter A, it's possible to use gravitation filtration.

E. Because of the volume is too small, such as letters B and C, the pressure filtration by a syringe filter is more indicate.

F. In this case, the filtration can be done by gravitation, and a vacuum can be added to accelerate it because is a small volume with solid impurities.

6 0

3 years ago

What can form as a result of a chemical reaction?

cestrela7 [59]

Answer is: new substance.

For example, synthesis chemical reaction: Ba + F₂ → BaF₂.

Synthesis reaction is a type of reaction in which multiple reactants combine to form a single product.

New substance, barium fluoride is formed, with different chemical and ohysical properties than reactants (barium and fluorine).

In barium fluoride, barium has oxidation number +2 and fluorine has oxidation number -1, so compound has neutral charge.

4 0

3 years ago

Read 2 more answers

Which of the following would lose heat the fastest?

Molodets [167]

Answer:

15 grams of water

Explanation:

15 grams of water of water would lose heat the faster compared to higher masses of water.

Water generally is a poor conductor heat.

To heat up a unit of water, significant amount of energy must be added to the body of water.
With time, the body continues to increase in temperature.
A 500g mass of water will take more time to lose heat.

5 0

3 years ago

4. Methane, CH4, is one carbon atom bonded to four hydrogen atoms. In order to show

oee [108]

The answer is C. the carbon symbol C with one dot on each

the top, bottom, left, and right sides

8 0

3 years ago