A chemist collects hydrogen gas over water in an apparatus shown below. If the eudiometer reads 17.3800 mL of gas and has a total pressure of 95.090 mm Hg at 15.0°C, then how many moles of hydrogen gas were collected? (the vapor pressure of water at 15.0°C is 12.8 mm Hg)

7.93 × 10⁻⁵ mol

Explanation:

Step 1: Calculate the pressure of hydrogen

The total pressure is the sum of the partial pressures of hydrogen and water vapor.

P = pH₂ + pH₂O

pH₂ = P - pH₂O

pH₂ = 95.090 mmHg - 12.8 mmHg = 82.3 mmHg

We can convert it to atm using the conversion factor 1 atm = 760 mmHg.

82.3 mmHg × 1 atm/760 mmHg = 0.108 atm

Step 2: Convert 15.0 °C to Kelvin

We will use the following expression.

K = °C + 273.15 = 15.0 + 273.15 = 288.2 K

Step 3: Calculate the moles of hydrogen

We will use the ideal gas equation.

P × V = n × R × T

n = P × V / R × T

n = 0.108 atm × 0.0173800 L / (0.0821 atm.L/mol.K) × 288.2 K

n = 7.93 × 10⁻⁵ mol

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.

answer: they produce more slow than unicellular organisms.