What is the formula for Volume?

Determine the ph of a 0. 35 m aqueous solution of CH3NH2 (methylamine). The kb of methylamine is?

guajiro [1.7K]

The pH of 0.35 M of CH₃NH₂ is 12.09 and the $k_b$ for methylamine is 4.4 x 10⁻⁴.

pHis the quantitative measure of acidity and basicity of an aqueous or other liquid solution. The scale range goes from 0 to 14. Water has a pH of 7 and is neutral in nature.

<h3>What is dissociation constant?</h3>

The dissociation constant is an equilibrium constant that describes the dissociation or ionization of a base or an acid

$k_a$ describes the dissociation of an acid

$k_b$ describes the dissociation of a base

For methylamine,

$CH_3NH_2 + H_2O\Leftrightarrow CH_3NH_3^+ + OH^-$

Initial concentration of methylamine = 0.35 M

Initial concentration of products = 0

Let, at equilibrium concentration of CH₃NH₂ = 0.35 - x

Then, concentration of CH₃NH₃⁺ and OH⁻ is x and x respectively

$k_b = \frac{[CH_3NH_3^+] [OH^-]}{[CH_3NH_2]}$

The dissociation constant for methylamine, $k_b$ = 4.4 x 10⁻⁴

$4.4 \times 10^-^4 = \frac{x.x}{0.35} \\x^{2} = 4.4 \times 10^-^4 \times 0.35\\x^{2} = 1.54 \times 10^-^4 \\$

$x =0.0124$

pOH = -log[OH] = -log(0.0124) = 1.91

pH + pOH = 14

pH = 14 - 1.91 = 12.09

Thus, the pH of methylamine is 12.09 and $k_b$ is 4.4 x 10⁻⁴

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7 0

2 years ago

1.A sample of pure calcium fluoride with a mass of 15.0 g contains 7.70 g of calcium. How much calcium is contained in 40.0 g of

QveST [7]

These are five questions and five answers.

1) Question 1. A sample of pure calcium fluoride with a mass of 15.0 g contains 7.70 g of calcium. How much calcium is contained in 40.0 g of calcium fluoride?

Answer:

20.5 g Ca

Explanation:

Calcium fluoride being a pure substance, has a fixed chemical compositon, which means that their elements (atoms), in any sample, are always in the same proportion.

Then, you can set the followoing proportion:

7.70 g Ca / 15.0 g CaF₂ = x / 40.0 g CaF₂

Now, solve for x:

x = 40.0 g CaF₂ × 7.70 g Ca / 15.0 g CaF₂ = 20.5 g Ca.

The answer must be expressed with 3 significan figures, since the three data are given with 3 significan figures.

2) Question 2. Silver has two isotopes. One isotope contains 60 neutrons and has a percent abundance of 51.839% the other contains 62 neutrons. Give the atomic symbols for the two isotopes.

Answer:

Isotope that contains 60 neutrons: ¹⁰⁷₄₇Ag

Isotope that contains 62 neutrons: ¹⁰⁹₄₇Ag

Explanation:

Isotopes are atoms of the same element, with different number of neutrons, so all the isotopes of an element have the same atomic number, Z (number of protons) and different mass number A (number of neutrons + protons).

The atomic symbols for isotopes uses the chemical symbol of the atom (Ag for silver); a subscript to the left of the chemical symbol that represents the atomic mass (47 for silver); and a superscript to the left of the chemical symbol that represents the mass number.

The mass number, A, for each silver isotope is calculated in this way:

Isotope that contains 60 neutrons: A = 60 + 47 = 107

Isotope that contains 62 neutrons: A = 62 + 47 = 109

Then, the respective atomic symboles are:

Isotope with 60 neutrons: ¹⁰⁷₄₇Ag

Isotope with 62 neutrons: ¹⁰⁹₄₇Ag

3) Question 3. What is the average atomic weight of silver? What is the mass (in grams) of a single chlorine molecule?

Answer:

107.96 amu

Explanation:

The atomic wieght of the elements is the weighted average weight of the different isotopes of the same element found in the nature, taking into account their relative abundance.

Average atomic weight = ∑( abundance × individual atomic weight)

Average atomic weight of silver = (abundace of isotope 1 × atomic weight isotope 1) + (abundance isotope 2 × atomic weight isotope 2)

Abundance isotope 1 = 51.839%

Atomic weight isotope 1 = mass number = 60 neutrons + 47 protons = 107 a.m.u
Abundance isotope 2 = 100% - 51.839% = 48.161%

Atomic weight isotope 2 = 62 neutrons + 47 protons = 109 a.m.u.

Average atomic weight of silve = 107 amu × 51.839% + 109 amu × 48.161% = 107.96 amu

4) Question without number: What is the mass (in grams) of a single chlorine molecule

Answer:

1.177 × 10⁻²² g

Explanation:

The chlorine molecule is diatomic. That means that each molecule contains two atoms. The chemical formula of chlorine molecule is Cl₂.

The mass of one mole of molecules of Cl₂ is 2 × 35.453 g/mol = 70.906 g/mol

Mass of a single molecule = mass of one mol / number of molecules in one mol

Mass of a single molecule = 70.906 g/mol / (6.022 × 10²³ molecules / mol)

Mass of a single molecule = 11.77 × 10⁻²³ g = 1.177 × 10⁻²² g

5) Question 4. How many moles of ethanol (CH₃CH₂OH) are in 141 mg?

Answer:

0.00301 mol

Explanation:

Molar mass of CH₃CH₂OH = 2 × 12.011 g/mol + 6 × 1.008 g/mol + 15.999 g/mol = 46.069 g/mol.

Formula: number of moles = mass in grams / molar mass

Calculation: number of moles = 141 mg × ( 1 g /1000 mg) / (46.069 g/mol = 0.00301 mol

4 0

3 years ago

3. Astronomers use various tools to gather evidence in support of the Big Bang

katrin [286]

The Big Bang theory is one of the ones used most frequently nowadays to describe how the cosmos came into being.

<h3>What does big bang theory state?</h3>

According to this theory, the universe formed 13.8 billion years ago as a result of the primordial atom, a single particle, exploding and generating an unprecedented cosmic disaster. The universe is always expanding, according to the same theory.

The key supporting data for the big bang theory are:

The galaxies to getting further and distant from us. This distance is taken at high speeds. In other words, the distance between galaxies is inversely correlated with their spacing velocity. Our perception of galaxy dysthanization occurs because the universe is continually expanding, according to this data, which is known as the "Hubble Law," and this hypothesis also explains that The cosmos has already been unified.

According to the big bang theory, the cosmos was extremely hot at the time of its creation; if this is accurate, we should find some proof of this warmth. Radio astronomers discovered this proof when they noticed that microwaves with a temperature of 2,725 degrees Kelvin included cosmic background radiation. This radiation is perhaps proof of the universe's high temperature.

Last but not least, the Big Bang most likely contributed to the abundance of hydrogen and helium elements.

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7 0

2 years ago

A sample of gas (1.3 mol) occupies __________ l at 22 Â°c and 2.5 atm.

Furkat [3]

To answer this question, you just need to put all the variable into PV = nRT formula. In this case, the pressure(P) is 2.5 atm, the number of molecule(n) is 1.3 mol, the temperature(T) is 22 celcius= 295.15 kelvin.
Then the volume should be:

PV = nRT
2.5 * V = 1.3 * 0.08206* 295.15
V= 12.59L

4 0

3 years ago

when a calcium atom loses its valence electrona the ion formed has an electron configuration that is the same as an atom of. (1)

andrew-mc [135]

(2) argon. This is because Ca originally has 20 total electrons with a configuration of 2,8,8,2. When it looses its valence electrons it remains with 18 electrons total (2,8,8 config). Argon has 18 electrons total too (2,8,8 config).

3 0

3 years ago

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