[JC531]

Hi chemfourm! I need some help. Basically my teacher is out for the week and we were given a packet to work from. It seems that it goes over the whole chapter so i'm expecting a test upon her return. I feel I know everything fairly well, the last things we did though i'm not exactly sure if I caught them in class. Because I'm expecting a test upon her return I have to make sure to get everything correct on this packet to ensure a grade > a 90 and a grade ≤ a 100. (I like 100s, I don't like 90s  , If I can get at least a 90 then I should be capable of 100 I like to think) Anyways the first few questions I had some trouble with despite solving them. I'm unsure if they are correct but I guess i'll post one and ask if it is correct first.

1. A gas collected when the pressure in 800.0 mm has a volume of 380 mL. What volume in milliliters will the gas occupy at standard pressure?
-for my answer I put 400 mL. A student in my class told me that mm is supposed to be mmHg so I solved it as if it was so. Yet I believe that this statement may be incorrect. To my knowledge there is no measurement of pressure using mm, or cm (from another question). Was my answer correct? Or was I mistaken and there is another way to solve it?

Also how would I convert something such as volume. temperature, and pressure into standard conditions? (I feel as if I know this but honestly have forgotten, a simple reminder should get me back on track)

One question for example is: Convert to standard conditions: 1520.0 mL of gas at -33.0°C and 720.0 mm pressure. How would I solve this?

[hamil]

Do you have a text book? Look up Standard Temperature and Pressure (STP)
Then, review the combined gas law.

[JC531]

I know what STP is. standard temperature and pressure. 1 atm and 0°C (or 273K). But, from my second question that I posted, how would I convert them to standard temperature and pressure. Do I just say that it is 0°C and the pressure 760mmHg? (or how would I solve this?) And what about for the 1520mL of gas?, how would I make this into standard conditions?

Thanx for replying btw! 

[billnotgatez]

If you are given starting volume, pressure, and temperature
If you are also given ending pressure and temperature
What is left to convert?

[Needaask]

I know what STP is. standard temperature and pressure. 1 atm and 0°C (or 273K). But, from my second question that I posted, how would I convert them to standard temperature and pressure. Do I just say that it is 0°C and the pressure 760mmHg? (or how would I solve this?) And what about for the 1520mL of gas?, how would I make this into standard conditions?

Thanx for replying btw! 

Is question 1 faulty? You are asked to convert into stp without knowing the temperature? Or do you assume that the temperature remains the same at 273K? Of so 400mmHg seems correct.

Now PV=nRT so PV/T is a constant as n and R remains the same. So you can get your new volume by substituting the variables.

[Borek]

1. A gas collected when the pressure in 800.0 mm has a volume of 380 mL. What volume in milliliters will the gas occupy at standard pressure?

[tex]P_1V_1 = P_2V_2[/tex]

P₁=800 mmHg, P₂=760 mmHg. You have to use standard pressure and assume temperature has not changed.

Convert to standard conditions: 1520.0 mL of gas at -33.0°C and 720.0 mm pressure. How would I solve this?

Calculate number of moles, calculate volume of that number of moles at STP.