Determine the molality of an aqueous solution that is 15.5 percent urea by mass.

1 answer:

3 0

15.5% by mass is equivalent 15.5 g urea in 100 g solution or 155 g urea in 1 kg solution. 

we know that molality = moles solute / kg solvent

moles solute = 155 g / 60 g/mol = 2.58 moles urea

Since there are 155 g urea in 1000g solution, hence the solvent is 845 g or 0.845 kg

So:
molality = 2.58 / 0.845 = 3.06 m

You might be interested in

Iron has a density of 7.86 g/cm3 (1 cm3=1 mL). Calculate the volume (in dL) of a piece of iron having a mass of 3.26 kg . Note t

Mkey [24]

$d=7,86\frac{g}{cm^{3}}=7,86\frac{0,001kg}{0,01dL}=0,786\frac{kg}{dL}\\
m=3,26kg\\\\\\
d=\frac{m}{V} \ \ \ \ \Rightarrow \ \ \ \ V=\frac{m}{d}=\frac{3,26kg}{0,786\frac{kg}{dL}}\approx4,15dL$

7 0

4 years ago

A sample of octane (c8h18 that has a mass of 0.750 g is burned in a bomb calorimeter. as a result, the temperature of the calori

timurjin [86]

In a closed system, heat should be conserved which means that the heat produced in the calorimeter is equal to the heat released by the combustion reaction. We calculate as follows:

Heat of the combustion reaction = mC(T2-T1)
= 1 (1.50) (41-21)
= 30 kJ

7 0

3 years ago

Read 2 more answers

Is light an external or internal stimulus for plant?explain how plants react to light

allochka39001 [22]

External

Stimuli are anything that causes arousal or enables an object to respond or react.

There are many different kinds of stimuli for which is different for every organism, for example, water, light and carbon dioxide are three stimuli and materials needed for photosynthesis in plants to manifest.
In humans, we have nutrients or food, oxygen and water for us to survive. These are stimuli, eyes need light as a stimuli for it see and function. Nasal receptors needs smell as stimuli caused by molecular reactions of an object as a stimuli. And others.

3 0

3 years ago

A 46.2 mL,0.568 M calcium nitrate solution is mixed with 80.5mL of 1.396M calcium nitrate solution.Calculate tge concentration o

Ne4ueva [31]

Answer:

1.09 M

Explanation:

Let's define the equation that will be used to calculate the final concentration of the resultant calcium nitrate solution. In order to calculate it, we need to find the total number of moles of calcium nitrate and divide by the total volume of the resultant solution:

$c=\frac{n}{V}$

This equation firstly helps us find the number of moles of calcium nitrate. Multiplying molarity by volume will yield the moles. Adding the moles from the first component to the second component will provide us with the total number of moles of calcium nitrate:

$n_{Ca(NO_3)_2}=46.2 mL\cdot0.568 M+80.5 mL\cdot1.396 M=138.62 mmol$