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

what are the two models

explanation:

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.