How Do You Calculate Moles in Biogas Composition?

[kecontroversy]

hi folks.. I am having some problem here, and i dun know how to solve it.. some mole calculation. i would like ask help from u guys.. many thanks.. questions are below: [can give me the working process in details?]

6. A report states that biogas is 60% methane (relative molecular mass = 16) and 40% carbon dioxide (relative molecular mass = 44) by weight. Consider 10 kg of biogas.
(a) How much methane, by weight, would you expect in 10 kg of biogas?

(b) How many moles of methane would be there in this biogas amount?

(c) How many moles of carbon dioxide would be there in this biogas amount?

(d) How many moles of biogas would there be in 10 kg of biogas?

(e) What is the pV content of 10 kg of biogas at 300 K?

 

[Moonbear]

You're going to have to show us your attempts first (even if they don't get the right answer) so we can determine where you are getting stuck to help. We won't do your homework for you.

If you're completely stuck and don't even know where to start, tell us what relative molecular mass is (understanding this is key to most of the questions you were asked).

 

[ravenprp]

Hi there,

Sure, I can help you with these mole calculations. Let's go through each question step by step.

(a) To find the weight of methane in 10 kg of biogas, we first need to calculate the total weight of biogas. Since biogas is 60% methane and 40% carbon dioxide, we can find the weight of biogas by multiplying 10 kg by 60% (0.60), which gives us 6 kg. This means that there are 6 kg of methane in 10 kg of biogas.

(b) To find the number of moles of methane in 10 kg of biogas, we need to use the formula: moles = mass/molar mass. The molar mass of methane is 16 g/mol. So, we can calculate the moles of methane by dividing 6 kg (which is 6000 g) by 16 g/mol. This gives us 375 moles of methane.

(c) Similarly, to find the number of moles of carbon dioxide in 10 kg of biogas, we can use the same formula. The molar mass of carbon dioxide is 44 g/mol. So, we divide 4 kg (which is 4000 g) by 44 g/mol. This gives us 90.9 moles of carbon dioxide.

(d) To find the total number of moles of biogas in 10 kg of biogas, we simply add the moles of methane and carbon dioxide. This gives us a total of 375 + 90.9 = 465.9 moles of biogas.

(e) To calculate the pV content of 10 kg of biogas at 300 K, we need to use the ideal gas law: PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the gas constant (0.0821 L atm/mol K), and T is the temperature in Kelvin. Since we know the number of moles (465.9) and the temperature (300 K), we can calculate the pV content by rearranging the equation to P = nRT/V. Plugging in the values, we get P = (465.9)(0.0821)(300)/V. Since we do not have the volume given, we cannot calculate the exact pV content