At 20.0 degrees celcius, a student collects H2 gas in a gas collecting tube. The barometric pressure is 755.2mm Hg and the water levels inside and outside the tube are exactly equal. What is the total gas pressure in the gas collecting tube?

Ptotal = 755.2mm = pH2O + pH2.

To determine the total gas pressure in the gas collecting tube, we need to consider the combined effect of the atmospheric pressure and the pressure caused by the collected H2 gas.

First, let's convert the given barometric pressure from mm Hg to atm. Since 1 atm is equivalent to 760 mm Hg, we can calculate the atmospheric pressure as follows:

Atmospheric pressure = 755.2 mm Hg / 760 mm Hg/atm ≈ 0.9947 atm

Next, we need to consider the pressure caused by the collected H2 gas. According to the Ideal Gas Law, the pressure (P) exerted by a gas is directly proportional to its temperature (T) and its molar amount (n), and inversely proportional to its volume (V):

P = (n * R * T) / V

Where:
P = pressure (in atm)
n = molar amount (in moles)
R = ideal gas constant (0.0821 L·atm/(mol·K))
T = temperature (in Kelvin)
V = volume (in liters)

Since we are given the temperature in degrees Celsius, we need to convert it to Kelvin. The Kelvin temperature can be calculated by adding 273.15 to the Celsius temperature:

T = 20.0°C + 273.15 = 293.15 K

To find the total gas pressure, we need to know the molar amount and volume of the collected H2 gas. The information given in the question does not provide these values. Therefore, without further data, we cannot determine the total gas pressure in the gas collecting tube.