1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
JulsSmile [24]
3 years ago
13

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

on?
Chemistry
1 answer:
ruslelena [56]3 years ago
3 0

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>
You might be interested in
Which is a positive effect of the technology advance of going from a compass to a gps
egoroff_w [7]

Answer:

Compass - Gps                              

Explanation:

I belive the pro's                                      and cons are

                                         GPS             you are trusting a little man made device

the direction you                               to give you directions

are going on                                        and that it won't break or die

a device not a paper map

                                                Compass

You can see north east south and              it is usually carefully crafted for                                                                                                                                                                          o                                                                     outdoors but it has no roads and

west on the compass and                          if given no directions, extremely

you can see the roads follow directions                  confusing until you learn it

like go south then east.

4 0
3 years ago
What is the maximum number of electrons in the first electron shell, closest to the nucleus?
Ymorist [56]
The correct answer is B. 2
6 0
3 years ago
Read 2 more answers
Butter melt when you heat it in a pan on the stove. Is this a chemical change or physical change? How can you tell?
choli [55]
It would be an physical change ; if you melt butter the butter goes from a solid to a liquid so therefore the physical state is changed.
4 0
3 years ago
What is the molarity of formaldehyde in a solution containing 0.25 grams of formaldehyde per mL?
Vikentia [17]

Answer:

8.33mol/L

Explanation:

First, let us calculate the molar mass of of formaldehyde (CH2O). This is illustrated below:

Molar Mass of CH2O = 12 + (2x1) + 16 = 12 + 2 + 16 = 30g/mol

Mass of CH2O from the question = 0.25g

Number of mole CH2O =?

Number of mole = Mass /Molar Mass

Number of mole of CH2O = 0.25/30 = 8.33x10^-3mole

Now we can calculate the molarity of formaldehyde (CH2O) as follow:

Number of mole of CH2O = 8.33x10^-3mole

Volume = 1mL

Converting 1mL to L, we have:

1000mL = 1L

Therefore 1mL = 1/1000 = 1x10^-3L

Molarity =?

Molarity = mole /Volume

Molarity = 8.33x10^-3mole/1x10^-3L

Molarity = 8.33mol/L

Therefore, the molarity of formaldehyde (CH2O) is 8.33mol/L

3 0
3 years ago
Mathias Schleiden, one of the writers of the cell theory, studied _________ tissue and noticed that every sample he looked at wa
JulijaS [17]
You need to put there “poetry “
8 0
3 years ago
Read 2 more answers
Other questions:
  • Assuming all gas is removed from the tank when filling balloons, how many 0.75 L balloons can be filled from a tank that contain
    14·2 answers
  • Which of the following numbers is correctly rounded to three significant figures, as shown in brackets?​
    8·1 answer
  • The process in which water changes its potential energy to kinetic energy as it moves from upstream to downstream is called load
    9·1 answer
  • Weight is measured using an instrument called a
    11·1 answer
  • Keeping the number of moles constant, what is the final pressure in atm if the temperature was cooled from -91.5°C to -239°C, th
    8·1 answer
  • What happens to the average kinetic energy of gas particles as the temperature increases?
    13·1 answer
  • What happens to the rate of the reaction as temperature increases
    13·1 answer
  • How many oxygen atoms are there in 0.25 mole of CO2?
    8·1 answer
  • You have 30.4 g of O2 gas in a container with twice the volume as one with CO2 gas. The pressure and temperature of both contain
    7·1 answer
  • What is the smallest unit of an element that retains the properties of that element?
    9·2 answers
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!