# Tank of pressurized air to loosen bolts

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1. Apr 6, 2015

### yassine

Car mechanics use compressed air tools to open bolts. Instead of using an air compressor one can also use a tank of pressurized air. There is an air tank with a volume of 50 L to work with. The pressure of the tank is 50 bars when it is stored indoors at 20 °C. The bolt wrench needs at least 10 bar pressure to operate. How long can the mechanics use the bolt wrench outdoors at -20 °C if it consumes 200 L/min of air at normal pressure? The normal pressure is 1.0 bar

2. Apr 6, 2015

3. Apr 6, 2015

### yassine

i haven't tried anything yet i found this on a entrance exam to a university and i've been stuck on it for a while

4. Apr 6, 2015

### Greg Bernhardt

What part are you stuck on? You must show some effort.

5. Apr 6, 2015

### yassine

i tried to use P(delta)V=nR(delta)T to calculate the change in pressure but since the problem lacks on n i can't do that

6. Apr 6, 2015

### Staff: Mentor

You know the volume of the tank, the initial temperature, and the initial pressure. From the ideal gas law, what is the initial number of moles n?

Chet