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natulia [17]
3 years ago
8

Question 14 A student dissolves 1.5g of styrene C8H8 in 225.mL of a solvent with a density of 1.02/gmL . The student notices tha

t the volume of the solvent does not change when the styrene dissolves in it. Calculate the molarity and molality of the student's solution. Round both of your answers to 2 significant digits. molarity = molality = Ă—10
Chemistry
2 answers:
Yuki888 [10]3 years ago
8 0

We must to know:

Cm = molarity = niu / Vs, when the niu = no. of moles and Vs = Volume of solution

the no. niu = mass / molecular mass of substance

molecular mass of C8H8 = 12x8+8x1 = 104 g/mol

=> niu = 1,5 / 104 = 0,0144 moles C8H8

=> Cm = 0,0144/0,225 = 0,06 mol/L

Cmm = molality = niu (C8H8) / mass of solvent (kg)

=> p = mass / V => mass (solvent) = p x V

=> 225 x 1,02 = 229,5 g solvent = 0,2295 kg solvent

=> Cmm = 0,0144 / 0,229,5 = 0,063

Nata [24]3 years ago
6 0

Answers:

a. 0.064 mol/L; b. 0.063 mol/kg

Explanation:

a. Molar concentration

c = moles/litres

=====

Moles = 1.5 × 1/104.15

Moles = 0.0144 mol

=====

Litres = 225. × 1/1000

Litres = 0.225. L

=====

c = 0.0144/0.225.

c = 0.064 mol·L⁻¹

===============

b. Molal concentration

b = moles of solute/kilograms of solvent

=====

Mass of solvent = 225. × 1.02/1

Mass of solvent = 229.5 g      Convert to kilograms

Mass of solvent = 0.2295 kg

=====

b = 0.0144/0.2295

b = 0.063 mol/kg

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Answer:

C) It has a constant average kinetic energy

Explanation:

The average kinetic energy of the particles in a gas is directly proportional to the temperature of the gas, according to the equation.

k is the Boltzmann's constant

T is the absolute temperature of the gas

Therefore, temperature of a gas is a measure of the average kinetic energy of the particles.

In this problem, we are told that the gas is at constant temperature (and volume): therefore, according to the previous equation, this means that the average kinetic energy is also constant.

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Where is the question
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λmax for the π → π* transition in ethylene is 170 nm. Is the HOMO-LUMO energy difference in ethylene greater than or less than t
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Answer:

the HOMO-LUMO energy difference in ethylene is greater than that of cis,trans−1,3−cyclooctadiene

Explanation:

The λmax is the wavelength of maximum absorption. We could use it to calculate the HOMO-LUMO energy difference as follows:

For ethylene

E= hc/λ= 6.63×10^-34×3×10^8/170×10^-9= 1.17×10^-18J

For cis,trans−1,3−cyclooctadiene

E= hc/λ=6.63×10^-34×3×10^8/230×10^-9=8.6×10^-19J

Therefore, the HOMO-LUMO energy difference in ethylene is greater than that of cis,trans−1,3−cyclooctadiene

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A 0.590 gram sample of a metal, M, reacts completely with sulfuric acid according to:M(s) +H2SO4(aq) --> MSO4(aq) +H2(g)A vol
photoshop1234 [79]

Answer:

MM = 58.41 g

Explanation:

First, the data we have is according to the hydrogen which is exerting pressure. To solve this, we need to use the ideal gas equation:

PV = nRT (1)

the molar mass of any compound is calculated like this:

MM = m/n (2)

So, from (1) we solve for the moles (n) and then, this value is replace in (2).

However, before we do all that, we need to gather all the correct data.

All the species in the reaction are solid or aqueous state, with the exception of hydrogen, which is gaseous. Hydrogen is collected over water, therefore, is exerting some pressure too. The problem is not indicating if the acid or any other species is exerting pressure, so we will assume that only hydrogen and water are exerting pressure.

The total pressure exerted by the system would be:

P = Pw + PH2 (3)

We already know the total pressure which is 756 torr.

This experiment is taking place at 25 °C (298.15 K), and at this temperature, we have a reported value for water pressure which is 23.8 Torr.

Let's solve for PH2:

PH2 = P - Pw

PH2 = 756 - 23 = 733 Torr

Now, with this value, and the volume and temperature, we can calculate the moles of H2:

n = PV/RT

But first, let's convert the pressure to atm:

PH2 = 733 Torr / 760 torr * 1 atm = 0.9644 atm

now, solving for n:

n = 0.9644 * (0.255) / 0.082 * 298.15

n = 0.0101 moles

Now that we have the moles, we know that the metal and the hydrogen has a mole ratio of 1:1 according to the reaction, so, this means that:

moles M = moles H2 = 0.0101 moles

We have the moles of the metal and the mass, we can calculate the molar mass using expression (2):

MM = 0.590/0.0101

MM = 58.41 g/mol

This is the molar mass of the metal

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Ulleksa [173]

Answer:

<h3>The answer is 320.75 mL</h3>

Explanation:

The volume of a substance when given the density and mass can be found by using the formula

volume =  \frac{mass}{density}  \\

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We have the final answer as

<h3>320.75 mL</h3>

Hope this helps you

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