# Molar mass, atm, pressure, find mass. HELP

• teggenspiller
In summary, Using the ideal gas law, n = PV/RT, and converting pressure to Pascals and temperature to Kelvin, we can calculate the number of moles of nitrogen in the container. Multiplying this number by the molar mass of nitrogen (28 g/mol) gives us the mass of nitrogen in grams. However, the given answer choices do not match the calculated value, suggesting that the initial values may have been modified.
teggenspiller

## Homework Statement

A nitrogen in the container (molar mass is 28 g/mol) has a pressure of 2.5 atm, a volume of 0.2 m3, and a temperature of 300C. What is the mass of the nitrogen?

## Homework Equations

first figure how many
moles there are

n=PV/RT

however, i need to use Pressure, Pa, and not in atmospheres.

## The Attempt at a Solution

how do i figure the pressure in Pa, and not atm. or can I use atm?
hmmmm

i did its 101.3 or 103.1. but either way i couldn't come up with correct answer... :( can u show me how to solve this.. ?

VP/RT
.2*253312.5/(8.31*303)= # of moles,
multiplied by 28 grams per mole

*(28)
563.37944

teggenspiller said:
i did its 101.3 or 103.1. but either way i couldn't come up with correct answer... :( can u show me how to solve this.. ?

Your methodology looked okay to me. Try again, posting your calculations step by step.

Notes:
1. 1 atm = 101,325 pascals or 101.3 kPa
2. Make sure that your temperature is absolute (Kelvin).

okay thank you. one minute.

P= (253312.5) Pa
R=8.31 J/(mol K)
V= in Liters of m^3??
V= .2m^3 or 200Liters
T= 273.15+30 = 303.15

(253312.5) * ( .2) / (8.31J/(mol K) *(303.15)=
1848175.32*28g/mol

=51748908.8

much too big

I thought that your temperature was 300C? You've used 30

The formula is n = p*v/(R*T) ; you have to divide by temperature, not multiply!

ha okay

jeez i completely missed that. thnaks!

i still am not geting the right thing? do i times the final answer by the grams/mol (28//)

teggenspiller said:
i still am not geting the right thing? do i times the final answer by the grams/mol (28//)

Yup. You should by now have n (from PV = nRT), and that's the number of moles. So number of moles multiplied by grams/mole will yield grams.

A. 125 g
B. 258 g
C. 421 g
D. 582 g
E. 864 g

teggenspiller said:
A. 125 g
B. 258 g
C. 421 g
D. 582 g
E. 864 g

I take it that these are the choices for answers to the question? If so, it looks to me like the correct answer corresponding to the initial values given in the problem statement is not in the list.

What final value for the grams of N2 did you calculate?

Is it possible that the starting values were modified to 'present a new problem'?

## 1. What is molar mass and how is it calculated?

Molar mass is the mass of one mole of a substance. It is calculated by adding the atomic masses of each element in a molecule or compound.

## 2. What is an atmosphere (atm) and how is it related to pressure?

An atmosphere is a unit of pressure equal to the average air pressure at sea level. It is commonly used to measure air pressure, which is the force exerted by the weight of air molecules in the atmosphere. One atmosphere is equal to 101,325 Pascals (Pa) or 14.7 pounds per square inch (psi).

## 3. How do I convert between different units of pressure?

To convert between different units of pressure, you can use a conversion factor. For example, to convert from atmospheres (atm) to Pascals (Pa), you would multiply the number of atmospheres by 101,325. To convert from Pascals to pounds per square inch (psi), you would multiply the number of Pascals by 0.000145.

## 4. How do I find the mass of a substance using its molar mass and the number of moles?

To find the mass of a substance, you can use the formula: mass = number of moles x molar mass. First, determine the number of moles by dividing the given mass by the molar mass. Then, multiply the number of moles by the molar mass to find the mass in grams.

## 5. Can you provide an example of using the Ideal Gas Law to calculate pressure?

Yes, the Ideal Gas Law is PV = nRT, where P is pressure (in Pa), V is volume (in m3), n is the number of moles, R is the gas constant (8.314 J/mol·K), and T is temperature (in K). For example, if we have 2 moles of gas in a container with a volume of 0.5 m3 at a temperature of 300 K, the pressure would be (2 mol x 8.314 J/mol·K x 300 K) / 0.5 m3 = 9972 Pa.

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