# Homework Help: How do you calculate kpa/min?

1. Jan 8, 2012

### huskyrunner5

How do you calculate kpa/min??

1. I am trying to find the rate of CO2 production in yeast fermentation. I used a gas pressure sensor to measure the kpa every minute. I recorded the initial kpa and the kpa after every minute for four minutes. I forgot how to calculate the kpa/min and need clarification

2. I think the equation is something like this:
Initial pressure - final pressure/ (seconds?) I doubt this is right

3. For instance, the initial pressure was 99.05 kpa and after a minute it was 99.03.
So would the rate be -.02 kPa/min?
Any help would be appreciated.

Last edited by a moderator: Jan 9, 2012
2. Jan 8, 2012

### Simon Bridge

Re: How do you calculate kPa/minute? Pleaaase help!

You plot a graph of pressure vs time and find the slope
(you have more than one data point so you may as well use them)

Quick-and-dirty method, take the difference between final and initial pressure readings, divide by 4mins.

Yes - do you need to worry about uncertainty? Best to take values farthest apart: it's change in pressure divided by change in time.
Measure changes in the units you need - so if you want kPa/min, measure pressure in kPa and time in mins ... if you need psi/decade, then...

3. Jan 9, 2012

### Staff: Mentor

Re: How so you calculate kpa/min??

Yes, that's the average rate of the pressure change for the first minute.