Question

Experiment 1 was repeated with 0.40 g of calcium, and the gas that evolved was collected. The identity of the gas, and its approximate volume at 1.0 atm and 27°C were:(Note: R = 0.0821 L•atm/mol•K) H2, 250 mL. H2, 500 mL. O2, 250 mL. O2, 500 mL.

Answer 1

The problem involves using the ideal gas law to determine the volume of hydrogen gas produced from the reaction of calcium with water. The correct answer is that hydrogen gas (H₂) with an approximate volume of 250 mL is evolved when 0.40 g of calcium reacts.

Step-by-step explanation:

The student is asking about the volume of gas evolved when calcium reacts, and the gas's identity. To solve this problem, we need to use the reaction of calcium with water and apply the ideal gas law:

• Ca(s) + 2H₂O(l) -> Ca(OH)₂(aq) + H₂(g)

Considering that calcium reacts with water to produce hydrogen gas (H₂), we will use the ideal gas equation PV = nRT to find the volume of hydrogen gas at 1.0 atm and 27°C (300.15 K).

First, we calculate the number of moles (n) of calcium:

• n = mass/Mr = 0.40 g / 40.08 g/mol = 0.00998 mol

Since 1 mol of Ca produces 1 mol of H₂, the moles of H₂ = moles of Ca = 0.00998 mol.

Next, we use the ideal gas law to find the volume (V):

• V = nRT/P
• V = (0.00998 mol)(0.0821 L•atm/mol•K)(300.15 K) / (1.0 atm)
• V ≈ 0.245 L or 245 mL

This approximate volume matches the option given of H₂, 250 mL, which indicates that this is the correct identity and volume of the gas collected.

Answer 2

The calculation using the ideal gas law and the stoichiometry of the reaction between calcium and water shows that 0.40 g of calcium produces approximately 250 mL of hydrogen gas (H2) at the given conditions of 1.0 atm and 27C.

Step-by-step explanation:

The subject of this question is Chemistry, specifically related to gas laws and stoichiometry. When calcium reacts with water, it produces hydrogen gas (H2) and calcium hydroxide. To calculate the approximate volume of the gas at specific conditions, we use the ideal gas law equation PV = nRT.

In this case, the number of moles (n) of hydrogen gas can be determined from the molar mass of calcium and the stoichiometry of the reaction, assuming complete reaction of 0.40 g of calcium, which is 0.01 moles (since the atomic weight of calcium is approximately 40 g/mole).

The ideal gas law then becomes V = (nRT)/P.

Converting the temperature to Kelvin (27°C + 273 = 300 K) and using the given value for R (0.0821 L•atm/mol•K), we calculate the volume. The calculated volume for hydrogen gas at 1.0 atm and 27°C is approximately 250 mL, which can be rounded to two significant figures due to the precision of the given mass of calcium.

Therefore, the correct answer is H2, 250 mL.