Methylamine HCl to 21% aqaous solution

[SonicNL]

Given​

(Credits to @G.Patton)
6.2g methylamine in 35mL water (prepared by adding a solution of 7.9g (198mmol) sodium hydroxide in 20mL cold water to a cooled solution of 13.5g methylamine HCl in 15mL water). This results in an 15% methylamine solution.


We want to scale this to yield a 21% methylamine solution. We want to know how much solution we can yield when 25kg methylamine HCI is used in this synthesis. The density of methylamine is 0.70 g/mL at 20 °C.


To scale the synthesis and determine the amount of solution that can be yielded when using 25 kg of methylamine HCl, we need to perform some calculations. Let's break it down step by step.

1. Calculate the moles of methylamine HCl used: The molar mass of methylamine HCl is 31.06 g/mol. Moles of methylamine HCl = mass / molar mass Moles of methylamine HCl = 25,000 g / 31.06 g/mol Moles of methylamine HCl = 804.67 mol
2. Calculate the moles of methylamine: Methylamine and methylamine HCl have a 1:1 stoichiometric ratio, so the moles of methylamine will be the same as the moles of methylamine HCl.
3. Calculate the volume of methylamine HCl solution used: The density of methylamine HCl is not provided, so we cannot directly convert the mass to volume. However, we can use the known concentration to calculate the volume. Given:
   • 13.5 g methylamine HCl
   • 15 mL water We can assume the density of the solution to be 1 g/mL. Total volume of methylamine HCl solution = 13.5 g + 15 mL = 28.5 mL
4. Calculate the volume of sodium hydroxide solution used: Given:
   • 7.9 g sodium hydroxide
   • 20 mL cold water Total volume of sodium hydroxide solution = 7.9 g + 20 mL = 27.9 mL
5. Calculate the total volume of the initial 15% methylamine solution: Total volume = volume of methylamine HCl solution + volume of sodium hydroxide solution + volume of water Total volume = 28.5 mL + 27.9 mL + 35 mL = 91.4 mL
6. Calculate the mass of methylamine used in the initial solution: Given:
   • 13.5 g methylamine HCl The molar mass of methylamine HCl is 31.06 g/mol, and the molar mass of methylamine is 31.06 g/mol - 36.46 g/mol = -5.40 g/mol. Mass of methylamine = moles of methylamine HCl × molar mass of methylamine Mass of methylamine = 13.5 g × (31.06 g/mol - 36.46 g/mol) / 31.06 g/mol Mass of methylamine = 13.5 g × 0.825 Mass of methylamine = 11.14 g
7. Calculate the concentration of the initial methylamine solution: Concentration = (mass of methylamine / total volume) × 100 Concentration = (11.14 g / 91.4 mL) × 100 Concentration = 12.17%

Now, let's proceed to scale up the synthesis to yield a 21% methylamine solution.

1. Calculate the desired mass of methylamine in the final solution: Given:
   • Desired concentration: 21%
   • Desired total volume: Unknown (let's call it V mL) Mass of methylamine = (21/100) × V mL × 0.70 g/mL
2. Set up an equation to solve for the unknown volume (V) using the desired concentration and the mass of methylamine: (mass of methylamine / V mL) × 100 = 21% (0.70 g/mL)

1. Calculate the desired mass of methylamine in the final solution: Given:
   • Desired concentration: 21%
   • Desired total volume: Unknown (let's call it V mL) Mass of methylamine = (21/100) × V mL × 0.70 g/mL
2. Set up an equation to solve for the unknown volume (V) using the desired concentration and the mass of methylamine: (mass of methylamine / V mL) × 100 = 21% (0.70 g/mL) × (mass of methylamine / V mL) × 100 = 21% (0.70 g/mL) × (mass of methylamine / V mL) = 0.21 0.70 × mass of methylamine = 0.21 × V mL V mL = (0.70 × mass of methylamine) / 0.21
3. Convert the volume from milliliters to liters: V liters = V mL / 1000

Now, let's substitute the known values and calculate the total solution volume in liters.
mass of methylamine = 25,000 g V mL = (0.70 × 25,000 g) / 0.21 V mL = 83,333.33 mL V liters = 83,333.33 mL / 1000 V liters ≈ 83.33 liters
Therefore, when using 25 kg of methylamine HCl in this synthesis, you can yield approximately 83.33 liters of a 21% methylamine solution.

The matrix is real.

 

[G.Patton]

Your calculations aren't correct. I answered it DM.

 

[SonicNL]

Thanks!