A glass labratory flask is filled with gas at 25 Deg C and 0.95 atm pressure, se

Question

A glass labratory flask is filled with gas at 25 Deg C and 0.95 atm pressure, sealed and then heated to 100 Deg C. What is the pressure inside the flask?  a) 0.70 atm  b) 0.05 atm  c) 1.19 atm  d) 1.24 atm e) 5.05 atm

How many moles of gas will occupy a volue of 0.75 L at a rtemperature of 347 K and a pressure of 2.5 atm? a) 7925 b) 0.066 c) 22.4 d) 0.11 e) 0.221

At a high altitude water boils at 90 Deg C instead of 100 Deg C as at sea leavel because the a) atmospheric pressure is greater b) atmospheric pressure is less c) Climate is cooler d) Hydrogen bonding is greater e) water is more saline

Explanation / Answer

1) Since it is glass flask, the volume is constant

So, we can use the relation P1/T1 = P2/T2

Here P1 and P2 are initial and final pressures

T1, T2are initial and final pressures

P1 = 0.95 atm, P2 = ?, T1= 298 K , T2 = 373 K

Substituting these values in above equation

0.95/P2 = 298/373

P2= 0.95 * 373/298 = 1.19 atm

So answer is c.

2) We will use ideal gas equation

PV = nRT

P = 2.5 atm R = 0.0821 L atm mol-1 K-1, V = 0.75 K, T =347 K

number of moles n = PV/RT = (2.5 * 0.75) / (0.0821 * 347 ) = 0.066 moles

Answer is b

3) Boiling point is the temperature at which vapor pressure of a substance is equal to atmospheric pressure. At high altitude the the atmospheric pressure is lower than sea level. So, water reaches atmospheric pressure at 90 C instead of 100 C.

So the answer is b

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