A gas has a volume of 1140 ml at 37 ºC and 620 mm Hg pressure. Calculate its volume at STP. 1.900
2.800
3.819
4.1000

3. 0.819L (819 mL)

Explanation: Before we go about solving this, we need to do some conversions prior to using the gas law, the gas law is as follows...

P(atm)*V(L)=n(mol)*r(constant)*T(in kelvin)

So here are all the conversions you need.

620 mm Hg -> 0.816 atm

1140 mL -> 1.14 L

37 C -> 310.15 K

After plugging in our new converted values, we will proceed to solve the number of moles of the gas present, our n value, so our equation will look like this...(Note: Constant r in this case is 0.08206 L*atm/K*mol)

(0.816 atm)(1.14 L) = n(0.08206)(310.15)

Solving for n we get 0.03653 moles.

Now our second part is to figure out the volume AT STP (standard temperature/pressure). In the STP conditions, your temperature defaults to 0 C (273.15 K) and 1 atm. Now there is an easier way to do this, but I'll also show the more comprehensive way. Here is the easier method...

Since 1 mole of every gas occupies 22.4 L at STP, we can simply multiply this by our number of moles. So (22.4L)(0.3653 mol) to give us 0.818272.

However, a more accurate answer can be given like this...

Plugging n back into the same equation and this time resetting pressure to 1 atm and temperature to 273.15 K and conserving our number of moles we get...

(1 atm)(v) = (0.03653 mol)(0.08206)(273.15 K)

v = (0.03653)(0.08206)(273.15)

v = 0.8188 L = 0.819 L or 819 mL

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).