Calculate the molality of a 20 by mass ammonium sulfate

Asked by wiki @ 12/06/2021 in Chemistry viewed by 881 People

Calculate the molality of a 20.0% by mass ammonium sulfate (nh4)2so4 solution. the density of the solution is 1.117 g/ml.

Answered by wiki @ 12/06/2021

Hello!

We have the following data:

m1 (solute mass) = 20 % m/m
M1 (Molar mass of solute) (NH4)2 SO4 = ?
m2 (mass of the solvent) = ? (in Kg)

First we find the solute mass (m1), knowing that:

20% m/m = 20g/100mL

20 ------ 100 mL (0,1 L)
y g --------------- 1 L

y = 20/0,1
y = 200 g --> m1 = 200 g

Let's find Solute's Molar Mass, let's see:

M1 of (Nh4)2SO4
N = 2*14 = 28
H = (2*4)*1 = 8
S = 1*32 = 32
O = 4*16 = 64
----------------------
M1 of (Nh4)2SO4 = 28+8+32+64 => M1 = 132 g/mol

We must find the volume of the solvent and therefore its mass (m2), let us see:

d = 1,117 g/mL
m = 200 g
v (volumen of solute) = ?

$d = \dfrac{m}{V} \to V = \dfrac{m}{d}$

$V = \dfrac{200\:\diagup\!\!\!\!g}{1,117\:\diagup\!\!\!\!g/mL} \to V = 179\:mL\:(volumen\:of\:solute)$

The solvent volume will be:

1000 -179 => V = 821 mL (volumen of disolvent)

If: 1 mL = 1g

Then the mass of the solvent is:

m2 (mass of the solvent) = 821 g → m2 (mass of the solvent) = 0,821 Kg

Now, we apply all the data found to the formula of Molality, let us see:

$\omega = \dfrac{m_1}{M_1*m_2}$

$\omega = \dfrac{200}{132*0,821}$

$\omega = \dfrac{200}{108,372}$

$\boxed{\boxed{\omega \approx 1,8\:Molal}}\end{array}}\qquad\checkmark$

_________________________________
_________________________________

Another way to find the answer:

We have the following data:

W (molality) = ? (in molal)
n (number of mols) = ?
m1 (solute mass) = 20 % m/m = 20g/100mL → (in g to 1L) = 200 g
m2 (disolvent mass) the remaining percentage, in the case: 80 % m/m = 800 g → m2 (disolvent mass) = 0,8 Kg
M1 (Molar mass of solute) (NH4)2 SO4
N = 2*14 = 28
H = (2*4)*1 = 8
S = 1*32 = 32
O = 4*16 = 64
----------------------
M1 of (Nh4)2SO4 = 28+8+32+64 => M1 = 132 g/mol

Let's find the number of mols (n), let's see:

$n = \dfrac{m_1}{M_1}$

$n = \dfrac{200}{132}$

$n \approx 1,5\:mol$

Now, we apply all the data found to the formula of Molality, let us see:

$\omega = \dfrac{n}{m_2}$

$\omega = \dfrac{1,5}{0,8}$

$
\boxed{\boxed{\omega \approx 1,8\:Molal}}\end{array}}\qquad\checkmark$

I hope this helps. =)

The mass number of an atom can be calculated from

Asked by wiki @ 10/11/2021 in Physics viewed by 334 persons

To find the number of neutrons in an atom, you would subtract A.) mass number from atomic number B.) atomic number from mass number C.) atomic number from electron number …

Calculate the percentage by mass of sodium in sodium bicarbonate

Asked by wiki @ 05/08/2021 in Chemistry viewed by 287 persons

(Need all boxes answered) Bicarbonate of soda (sodium hydrogen carbonate) is used in many commercial preparations. Its formula is NaHCO3. Find the mass percentages (mass %) of Na, H, C, …

Calculate the mass of sodium acetate that must be added

Asked by wiki @ 02/08/2021 in Chemistry viewed by 265 persons

How many grams of sodium acetate ( molar mass = 83.06 g/mol ) must be added to 1.00 Liter of a 0.200 M acetic acid solution to make a buffer …

A hydrate of magnesium sulfate has a mass of 13.52

Asked by wiki @ 11/06/2021 in Chemistry viewed by 246 persons

A hydrate of magnesium sulfate has a mass of 13.52 g. The sample is heated until no water remains. The anhydrate has a mass of 6.60 g. Find the formula …

Calculate the molar mass for mn2o3 an oxide of manganese

Asked by wiki @ 12/07/2022 in Chemistry viewed by 144 persons

Calculate the molar mass for Mn2O3, an oxide of manganese.

What is the molar mass of iron ii sulfate feso4

Asked by wiki @ 04/12/2021 in Chemistry viewed by 325 persons

What mass of FeSO4^2- x 6H20 (Molar Mass=260g/mol) is required to produce 500 mL of a .10M iron (II) sulfate solution. A.) 9g B.) 13g C.) 36g D.) 72g

What is the molar mass of copper ii sulfate cuso4

Asked by wiki @ 30/11/2021 in Chemistry viewed by 436 persons

An aqueous solution is 15.0% by mass of copper(II) sulfate pentahydrate, CuSO4∙5H2O.What is the molarity of CuSO4 in this solution at 20°C?The density of this solution at 20°C is1.167g/mL(molecular weight …

How to calculate the molar mass of an unknown gas

Asked by wiki @ 22/11/2021 in Chemistry viewed by 431 persons

The molar mass of unknown gas was measured by effusion experiment. it was found that it took 63s for the gas to effuse, whereas nitrogen gas required 48s. what is …

Calculate the mass of 6.9 moles of nitrous acid hno2

Asked by wiki @ 29/10/2021 in Chemistry viewed by 315 persons

The value of Ka for nitrous acid (HNO2) at 25 ∘C is 4.5×10−4 .a. Write the chemical equation for the equilibrium that corresponds to Ka1. H+(aq)+NO−2(aq)⇌HNO2(aq)2. HNO2(aq)⇌H+(aq)+NO−2(aq)3. HNO2(aq)⇌H−(aq)+NO+2(aq)4. HNO2(aq)+H+(aq)⇌H2NO+2(aq)5. HNO2(aq)+H−(aq)⇌H2NO+2(aq)b. …

What is the mass of 3.45 moles of aluminum sulfate

Asked by wiki @ 29/07/2021 in Chemistry viewed by 233 persons

How many particles are in 3.55 moles of Aluminum Sulfate

The mass of 1.21 x10 20 atoms of sulfur is

Asked by wiki @ 02/07/2021 in Chemistry viewed by 680 persons

What is the mass of 2.23 x 10 to the 23rd atoms of sulfur?

Calculate the atomic mass of silicon the three silicon isotopes

Asked by wiki @ 12/06/2021 in Chemistry viewed by 273 persons

Calculate the atomic mass of silicon. The three silicon isotopes have atomic masses and relative abundances of 27.9769 amu (92.2297%), 28.9765 amu (4.6832%) and 29.9738 amu (3.0872%). Show your work.