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ICE Princess25 [194]

2 years ago

5

An unidentified compound contains only phosphorous and fluorine, meaning we could write its formula as PxFy. Heating 0.2324 g of

the compound in a 378-mL container converted all of it to gas with a pressure of 97.3 torr at 77°C. The gaseous PxFy was then reacted with an aqueous solution of calcium chloride, and all of the fluorine was converted to 0.2631 g of CaF2. Find the molecular formula of the compound.

1 answer:

cricket20 [7]2 years ago

4 0

Answer:

The molecular formula of the compound is P2F4

Explanation:

Step 1: Data given

Mass of the compound = 0.2324 grams

Volume of container = 378 mL

Pressure at 77 °C = 97.3 torr

The gaseous PxFy was then reacted with an aqueous solution of calcium chloride, and all of the fluorine was converted to 0.2631 g of CaF2.

Molar mass CaF2 = 78.07 g/mol

Step 2: Calculate moles CaF2

Moles CaF2 = 0.2631 g/ 78.07 g/mol=0.003370

Step 3: Calculate moles F

For every 1 mol CaF2 we have 1 mol Ca2+ and 2 moles F-

moles F- = 2 * 0.003370=0.006740

Step 4: Calculate mass of F

mass F = 0.006740 mol * 19.00 g/mol=0.1281 g

Step 5: Calculate mass of P

mass P = mass of compound - mass of F = 0.2324 - 0.1281 =0.1043 g

Step 6: Calculate moles P

moles P = 0.1043 g/ 30.97 g/mol=0.003368 moles

Step 7: Calculate mol ratio

We divide by the smallest amount of moles

P: 0.003368/0.003368 =1

F: 0.006740/ 0.003368 =2

The empirical formula is PF2

The empirical formula has a molar mass of 68.97 g/mol

Step 8: Calculate moles of compound

p*V = n*R*T

n = (p*V)/(R*T)

⇒ with p = the pressure of the gas = 97.3 torr = 97.3/760 = 0.128 atm

⇒ with V = the volume of the gas = 0.378 L

⇒ with R = the gas constant = 0.08206 L*atm/K*mol

⇒ with T = the temperature = 77.0 °C = 350 Kelvin

Number of moles =(0.128 *0.378)/(0.08206*350)

Number of moles =

moles gas = pV/RT = 0.128 atm x 0.378 dm^3/ 0.08206x350 K=0.00168

Step 9: Calculate molar mass

Molar mass = mass / moles

Molar mass = 0.2324 grams / 0.00168 moles

Molar mass = 138 g/mol

Step 10: Calculate the molecular formula

138.0 / 68.97 = 2

2*(PF2) = P2F4

The molecular formula of the compound is P2F4

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An element is a pure substance in which there are how many kinds of atoms?

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Answer:

One

Explanation:

An element is a pure substance in which there are only one kind of atom. Elements are distinct substances that cannot be split up into simpler substances.

Such substances consists of only one kind of atom. There are over a hundred known elements to date.

Generally, as a pure substance, the composition of an element is definite and they are homogenous in all parts.

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A sample of neon has a volume of 40.81 m3 at 23.5C. At what temperature, in Kelvins, would the gas occupy 50.00 cubic meters? As

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At $\fbox{\begin \\363 K \end{minispace}}$ temperature, a sample of neon gas will occupy $50.00 \text{ m}^{3}$ volume.

Further Explanation:

The given problem is based on the concept of Charles’ law. Charles’ law states that “at constant pressure and fixed mass the volume occupied an ideal gas is directly proportional to the Kelvin temperature.”

Mathematically the law can be expressed as,

$\fbox{ \begin \\ V \propto T \end{minispace}}$

Or,

$\frac{V}{T}=k$

Here, <em>V</em> is the volume of the gas, <em>T</em> is Kelvin temperature, and <em>k</em> is proportionality constant.

Given information:

The initial volume of neon gas is $40.81 \text{ m}^{3}$ .

The final volume of neon gas is $50.00 \text{ m}^{3}$ .

The initial temperature value is $23.5 \text{ } ^{\circ} \text{C}$ .

To calculate:

The final temperature

Given Condition:

The pressure is constant.

Mass of gas is fixed.

Solution:

Step 1: Modify the mathematical expression for Charles’ law for two different temperature and volume values as follows:

$\frac{V_{1}}{T_{1}}=\frac{V_{2}}{T_{2}}$

Here,

$V_{1}$ is the initial volume of the gas.

$V_{2}$ is the final volume of the gas.

$T_{1}$ is the initial temperature of the gas.

$T_{2}$ is the final temperature of the gas.

Step 2: Rearrange equation (2) for .

$\fbox {\begin \\T_{2}=\frac{(V_{2}) \times (T_{1})}{V_{1}}\\\end{minispace}}$ …… (2)

Step 3: Convert the given temperature from degree Celsius to Kelvin.

The conversion factor to convert degree Celsius to Kelvin is,

$T(\text{K}) = T(^{\circ}\text{C}) + 273.15$ …… (3)

Substitute $23.5\text{ }^{\circ} \text{C}$ for $T(^{\circ}\text{C})$ in equation (3) to convert temperature from degree Celsius to Kelvin.

$T(\text{K}) = 23.5 \text{ } ^{\circ} \text{C} + 273.15\\T(\text{K})= 296.65 \text{ K}$

Step 4: Substitute $40.81 \text{ m}^{3}$ for $V_{1}$ , $50.00 \text{ m}^{3}$ for $V_{2}$ and $296.65 \text{ K}$ for $T_{1}$ in equation (2) and calculate the value of $T_{2}$ .

$T_{2}=\frac{(50.00 \text{ m}^{3}) \times (296.65 \text{ K})}{40.81 \text{ m}^{3}}\\T_{2}=363.45 \text{ K}\\T_{2} \approx 363 \text{ K}$

Important note:

The temperature must be in Kelvin.

The condition of fixed mass and fixed pressure must be fulfilled in order to apply Charles’ law.

Learn More:

1. Gas laws brainly.com/question/1403211

2. Application of Charles’ law brainly.com/question/7434588

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: States of matter

Keywords: neon, volume, occupies, temperature, Kelvin, degree Celsius, Charle’s law, constant pressure, fixed mass, 40.81 m^3 , 50.00 m^3 , 23.5 degree C , celsius , 363 K , sates of matter, initial volume, final volume, initial temperature, final temperature, V1 , V2 , T1 , T2 .

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jeka94

Answer:

3. The mass of ethanol required is approximately 0.522869 g

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Explanation:

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