Matter cannot be created or _________

An aqueous solution of methylamine (ch3nh2) has a ph of 10.68. how many grams of methylamine are there in 100.0 ml of the soluti

ruslelena [56]

Answer:

3.4 mg of methylamine

Explanation:

To do this, we need to write the overall reaction of the methylamine in solution. This is because all aqueous solution has a pH, and this means that the solutions can be dissociated into it's respective ions. For the case of the methylamine:

CH₃NH₂ + H₂O <-------> CH₃NH₃⁺ + OH⁻ Kb = 3.7x10⁻⁴

Now, we want to know how many grams of methylamine we have in 100 mL of this solution. This is actually pretty easy to solve, we just need to write an ICE chart, and from there, calculate the initial concentration of the methylamine. Then, we can calculate the moles and finally the mass.

First, let's write the ICE chart.

CH₃NH₂ + H₂O <-------> CH₃NH₃⁺ + OH⁻ Kb = 3.7x10⁻⁴

i) x 0 0

e) x - y y y

Now, let's write the expression for the Kb:

Kb = [CH₃NH₃⁺] [OH⁻] / [CH₃NH₂]

We can get the concentrations of the products, because we already know the value of the pH. from there, we calculate the value of pOH and then, the OH⁻:

The pOH:

pOH = 14 - pH

pOH = 14 - 10.68 = 3.32

The [OH⁻]:

[OH⁻] = 10^(-pOH)

[OH⁻] = 10^(-3.32) = 4.79x10⁻⁴ M

With this concentration, we replace it in the expression of Kb, and then, solve for the concentration of methylamine:

3.7*10⁻⁴ = (4.79*10⁻⁴)² / x - 4.79*10⁻⁴

3.7*10⁻⁴(x - 4.79*10⁻⁴) = 2.29*10⁻⁷

3.7*10⁻⁴x - 1.77*10⁻⁷ = 2.29*10⁻⁷

x = 2.29*10⁻⁷ + 1.77*10⁻⁷ / 3.7*10⁻⁴

x = [CH₃NH₂] = 1.097*10⁻³ M

With this concentration, we calculate the moles in 100 mL:

n = 1.097x10⁻³ * 0.100 = 1.097x10⁻⁴ moles

Finally to get the mass, we need to molar mass of methylamine which is 31.05 g/mol so the mass:

m = 1.097x10⁻⁴ * 31.05

<h2>m = 0.0034 g or 3.4 mg of Methylamine</h2>

3 0

3 years ago

A compressed gas cylinder is filled with 5270 g of argon gas. The pressure inside the cylinder is 2050 psi at a temperature of 1

LuckyWell [14K]

Answer:

A compressed gas cylinder is filled with 5270 g of argon gas.

The pressure inside the cylinder is 2050 psi at a temperature of 18C.

The valve to the cylinder is opened and gas escapes until the pressure inside the cylinder is 650. psi and the temperature are 26 C.

How many grams of argon remains in the cylinder?

Explanation:

First, calculate the volume of argon gas that is present in the gas cylinder by using the ideal gas equation:

Mass of Ar gas is --- 5270g.

The number of moles of Ar gas:

$Number of moles of Ar gas=\frac{given mass of Ar}{its atomic mass} \\ =\frac{5270g}{39.948g/mol} \\ =131.9mol$

Temperature T=(18+273)K=291K

Pressure P=2050psi

$2050* 0.0680atm\\\\=139.4atm\\$

Volume V=?

$PV=nRT\\139.4atm * V=131.9mol *0.0821L.atm.mol-1.K-1 * 291K\\=>V=\frac{131.9mol *0.0821L.atm.mol-1.K-1 * 291K}{139.4atm} \\=>V=22.6L$

Using this volume V=22.6L

Pressure=650psi=44.2atm

Temperature T= (26+273)K=299K

calculate number of moles "n" value:

$PV=nRT\\=>n=\frac{PV}{RT} \\=>n=\frac{44.2atm*22.6L}{0.0821L.atm.mol^-1K^-1* 299K} \\=>n=40.7mol$

Mass of 40.7mol of Ar gas:

$mass of Ar gas=number of moles * its atomic mass\\\\ =40.7mol* 39.948g/mol\\\\ =1625.8g$

Answer:

The mass of Ar gas becomes 1625.8g.

8 0

3 years ago

Which of the following work mostly severaly affect a human population

Arada [10]

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6 0

3 years ago

What is the [H+] of a solution with a pH of 9.40?

LiRa [457]

Answer:

a) 3.98 x 10^-10

Explanation:

Hello,

In this case, for the given pH, we can compute the concentration of hydronium by using the following formula:

$pH=-log([H^+])$

Hence, solving for the concentration of hydronium:

$[H^+]=10^{-pH}=10^{-9.40}\\$

$[H^+]=3.98x10^{-10}M$

Therefore, answer is a) 3.98 x 10^-10

Best regards.

4 0

3 years ago

Given that the density of water is 1.00 g/mL, the density of toluene is 0.867 g/mL, and the density of chloroform is 1.48 g/mL,

12345 [234]

Answer:
Top-Toluene
Middle-Water
Bottom-Chloroform

Explication:
Chloroform is on the bottom layer because it is the densest liquid.
Toluene is on the top because it is the least dense.
Water is between the two because it’s density is between chloroform and toluene.

4 0

3 years ago

Matter cannot be created or __________.