Predict whether each substance will dissolve in water.

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

Determine the length of the object shown <br>A. 97.8 mm<br>B. 97.80 mm<br>C. 97 mm<br>D. 98 mm

jeka94

Answer:

A. 97.8 mm

Explanation:

There are 10 divisions between 9 cm (90 mm) and the end of the ruler (10 cm or 100 mm).

Each division equals 1 mm.

Each 5 mm mark has a longer tick, and the dashed red line is between the 97 mm and 98 mm marks.

You would normally estimate to the nearest tenth of a division. An estimate of 0.8 mm is reasonable.

The length of the object is 97.0 mm + 0.8 mm = 97.8 mm.

B is wrong. You can't possibly estimate to the nearest hundredth of a division.

C is wrong. The dashed red line slightly before the 98 mm mark.

D is wrong. If the dashed red line were exactly on the 98 mm mark, you would record the measurement as 98.0 mm. This indicates that you measured the object to zero tenths on either side of the mark.

6 0

2 years ago

Is c7h16+o2→co2+8h2o+7co2 a balanced equation

erik [133]

<span>C7H16 + 11 O2 = 7 CO2 + 8 H2O

If you write it like this then it is balanced.</span>

7 0

3 years ago

If O2 molecule is saturated with outer electrons how can it gain electrons to form ions?

PIT_PIT [208]

Answer: it will gain them by multiplying the electrons

Explanation:

its like 2 + 2=4

4+4=8

8 0

2 years ago

The element X has three naturally occurring isotopes. The masses (amu) and % abundances of the isotopes are given in the table b

denis-greek [22]

Answer:

220.42098 amu

Explanation:

(220 .9 X .7422) + (220 X .0.1278) + (218.1 X 0.13) = 220.42098 amu

These are weighted averages.

So, we will take mass of one and multiply by abundance percentage that is provided and add them together.

In order to calculate the average atomic mass, we have to convert the percentages of abundance to decimals. So, you get

(220 .9 X .7422) + (220 X .0.1278) + (218.1 X 0.13) = 220.42098 amu

6 0

2 years ago