1. Dada la reacción: C2

Describe how you would prepare exactly 100 mL of 0.109 M picolinate buffer, pH 5.61. Possible starting materials are pure picoli

Pepsi [2]

Answer:

1.342g of picolinic acid and 6.743mL of 1.0M NaOH diluting the mixture to 100.0mL

Explanation:

<em>The pKa of the picolinic acid is 5.4.</em>

Using Henderson-Hasselbalch formula for picolinic-picolinate buffer:

pH = pKa + log [Picolinate] / [Picolinic]

<em>Where [] could be taken as moles of each species</em>

<em />

5.61 = 5.4 + log [Picolinate] / [Picolinic]

0.21 = log [Picolinate] / [Picolinic]

1.62181 = [Picolinate] / [Picolinic] <em>(1)</em>

Now, both picolinate and picolinic acid will be:

0.100L * (0.109mol / L) =

0.0109 moles = [Picolinate] + [Picolinic] <em>(2)</em>

First, as we will start with picolinic acid, we need add:

0.0109 moles picolinic acid * (123.10g/mol) = 1.342g of picolinic acid

Now, replacing (2) in (1):

1.62181 = 0.0109 moles - [Picolinic] / [Picolinic]

1.62181 [Picolinic] = 0.0109 moles - [Picolinic]

2.62181 [Picolinic] = 0.0109 moles

[Picolinic] = 4.157x10⁻³ moles

And:

[Picolinate] = 0.0109 - 4.157x10⁻³ moles =

<h3>6.743x10⁻³ moles</h3><h3 />

To obtain these moles of picolinate ion we need to make the reaction of the picolinic acid with NaOH:

Picolinic acid + NaOH → Picolinate + Water

<em>That means to obtain 6.743x10⁻³ moles of picolinate ion we need to add 6.743x10⁻³ moles of NaOH</em>

<em />

6.743x10⁻³ moles of NaOH that is 1.0M are, in mL:

6.743x10⁻³ moles * (1L / 1mol) = 6.743x10⁻³L * 1000 =

<h3>6.743mL of the 1.0M NaOH must be added</h3><h3 />

Thus, we obtain the desire moles of picolinate and picolinic acid to obtain the buffer we want, the last step is:

<h3>Dilute the mixture to 100mL, the volume we need to prepare</h3>

3 0

2 years ago

(ii) When shale gas is burned, the hydrogen sulfide reacts with oxygen.

Elenna [48]

Answer:

See explanation

Explanation:

Now , we have the equation of the reaction as;

2H2S(g) + 302(g)------->2SO2(g) + 2H2O(g)

This equation shows that SO2 gas is produced in the process. Let us recall that this same SO2 gas is the anhydride of H2SO4. This means that it can dissolve in water to form H2SO4

So, when SO2 dissolve in rain droplets, then H2SO4 is formed thereby lowering the pH of rain water. This is acid rain.

4 0

2 years ago

Select the statement(s) that explain(s) the relationship between the arrangement of elements by size and first ionization energy

kow [346]

c. A full s subshell is able to shield a newly filled p subshell from the nucleus, making the first electron in a p subshell easy to remove.

Explanation:

From the given options, a full s-sublevel is able to shield a newly filled p-subshell from the nucleus thereby making the first electron in a p-subshell easy to remove is correct.

What is ionization energy?

Ionization energy is a measure of the readiness of an atom to lose an electron.

First ionization energy is the energy required to remove the most loosely held electron in the gas phase.

The size of an atom/element depends on the number of electrons it contains. The more the electrons, the larger its size.

The larger an atom becomes the lesser the ionization energy needed to remove the first electron from its outermost shell.

Electron - electron repulsion occurs when two electrons in the same sub-level repels one another.

Shielding effect is the ability of the inner electrons to protect the outer electrons from the pull of the nuclear charge.

In option C, a s-subshell has a greater shielding effect than the p,d and f sub-shell in that order.

A newly introduced electron in the p-sublevel will be loosely held and easier to remove.

Learn more:

First ionization energy brainly.com/question/2153804

#learnwithBrainly

8 0

2 years ago

Read 2 more answers

When iron pyrite (FeS2) is heated in air, the process known as "roasting" forms sulfur dioxide and iron(III) oxide. When the equ

Ronch [10]

Answer:

The coefficient of O2 is 11

Explanation:

Step 1:

The equation for the reaction:

FeS2 + O2 → SO2 + Fe2O3

Step 2:

Balancing the equation. The equation can be balance as follow:

FeS2 + O2 → SO2 + Fe2O3

There are 2 atoms of Fe on the right side and 1 atom on the left. It can be balance by putting 2 in front of FeS2 as shown below:

2FeS2 + O2 → SO2 + Fe2O3

There are 4 atoms of S on the left side and 1 atom on the right side. It can be balance by putting 4 in front of SO2 as shown below:

2FeS2 + O2 → 4SO2 + Fe2O3

Now, there are a total of 11 atoms of O on the right side and 2 atoms on the left side. It can be balance by putting 11/2 in front of O2 as shown below:

2FeS2 + 11/2O2 → 4SO2 + Fe2O3

Multiply through by 2 to clear the fraction as shown below:

4FeS2 + 11O2 → 8SO2 + 2Fe2O3

Now the equation is balanced.

The coefficient of O2 is 11

8 0

2 years ago

A 20.0-mL sample of lake water was acidified with nitric acid and treated with excess KSCN to form a red complex (KSCN itself is

Novosadov [1.4K]

Answer:

8.09x10⁻⁵M of Fe³⁺

Explanation:

Using Lambert-Beer law, the absorbance of a sample is proportional to its concentration.

In the problem, the Fe³⁺ is reacting with KSCN to produce Fe(SCN)₃ -The red complex-

The concentration of Fe³⁺ in the reference sample is:

4.80x10⁻⁴M Fe³⁺ × (5.0mL / 50.0mL) = 4.80x10⁻⁵M Fe³⁺

<em>Because reference sample was diluted from 5.0mL to 50.0mL.</em>

<em>That means a solution of 4.80x10⁻⁵M Fe³⁺ gives an absorbance of 0.512</em>

Now, as the sample of the lake gives an absorbance of 0.345, its concentration is:

0.345 × (4.80x10⁻⁵M Fe³⁺ / 0.512) = <em>3.23x10⁻⁵M. </em>

As the solution was diluted from 20.0mL to 50.0mL, the concentration of Fe³⁺ in Jordan lake is:

3.23x10⁻⁵M Fe³⁺ × (50.0mL / 20.0mL) = <em>8.09x10⁻⁵M of Fe³⁺</em>

4 0

2 years ago