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3 years ago

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

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Answer: The molar mass of the gas is 9.878 g/mol.

Explanation:

According to Graham's law, the rate of diffusion is inversely proportional to square root of molar mass of gas.

$Rate = \frac{1}{\sqrt{M}}$

where,

M = molar mass of gas

As given gas diffuses 1/7 times faster than hydrogen gas. So, its molar mass is calculated as follows.

$\frac{R_{1}}{R_{2}} = \sqrt{\frac{M_{2}}{M_{1}}}\\$

where,

$M_{1}$ = molar mass of hydrogen gas

$M_{2}$ = molar mass of another given gas

$R_{1}$ = rate of diffusion of hydrogen

$R_{2}$ = rate of diffusion of another given gas = $\frac{1}{7}R_{1}$

Substitute the values into above formula as follows.

$\frac{R_{1}}{R_{2}} = \sqrt{\frac{M_{2}}{M_{1}}}\\\frac{R_{1}}{\frac{1}{7}R_{1}} = \sqrt{\frac{M_{2}}{2}}\\7 \times 1.414 = M_{2}\\M_{2} = 9.878 g/mol$

Thus, we can conclude that the molar mass of the gas is 9.878 g/mol.

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3 years ago

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Osmium metal, the densest element, has a density of 22.6 g/mL, while hydrogen, the least dense element, has a density of 8.99 e-

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Answer:

1. Volume of osmium = 0.044 mL

2. Volume of Hydrogen = 11123.47 mL

3. Osmium is 251390 times denser than hydrogen

Explanation:

From the question given above, the following data were obtained:

Density of osmium = 22.6 g/mL

Density of Hydrogen = 8.99×10¯⁵ g/mL

Mass of osmium = 1 g

Mass of Hydrogen = 1 g

1. Determination of the Volume of osmium.

Density of osmium = 22.6 g/mL

Mass of osmium = 1 g

Volume of osmium =?

Density = mass /volume

22.6 = 1 / volume

Cross multiply

22.6 × volume = 1

Divide both side by 22.6

Volume = 1 / 22.6

Volume of osmium = 0.044 mL

2. Determination of the Volume of Hydrogen.

Density of osmium = 8.99×10¯⁵ g/mL

Mass of osmium = 1 g

Volume of osmium =?

Density = mass /volume

8.99×10¯⁵ = 1 / volume

Cross multiply

8.99×10¯⁵ × volume = 1

Divide both side by 8.99×10¯⁵

Volume = 1 / 8.99×10¯⁵

Volume of Hydrogen = 11123.47 mL

3. Determination of the number of times osmium is denser than hydrogen.

Density of osmium (Dₒ) = 22.6 g/mL

Density of Hydrogen (Dₕ) = 8.99×10¯⁵ g/mL

Dₒ / Dₕ = 22.6 / 8.99×10¯⁵

Dₒ / Dₕ = 251390

Cross multiply

Dₒ = 251390 × Dₕ

Thus, osmium is 251390 times denser than hydrogen.

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2 years ago