Answer:
2.4 g
Explanation:
Step 1: Given data
- Initial pressure (P₁): 755 torr
- Final pressure (P₂): 1.87 atm
Step 2: Convert "P₁" to atm
We will use the conversion factor 1 atm = 760 torr.
755 torr × 1 atm/760 torr = 0.993 atm
Step 3: Convert "T" to K
We will use the following expression.
K = °C + 273.15
K = 25°C + 273.15 = 298 K
Step 4: Calculate the initial number of moles of He
We will use the ideal gas equation.
P₁ × V = n₁ × R × T
n₁ = P₁ × V/R × T
n₁ = 0.993 atm × 16.8 L/(0.0821 atm.L/mol.K) × 298 K
n₁ = 0.682 mol
Step 5: Calculate the final number of moles of He
We will use the ideal gas equation.
P₂ × V = n₂ × R × T
n₂ = P₂ × V/R × T
n₂ = 1.87 atm × 16.8 L/(0.0821 atm.L/mol.K) × 298 K
n₂ = 1.28 mol
Step 6: Calculate the moles of He added
n = n₂ - n₁
n = 1.28 mol - 0.682 mol
n = 0.60 mol
Step 7: Convert "n" to mass
The molar mass of He is 4.00 g/mol
0.60 mol × 4.00 g/mol = 2.4 g
D because 0 is always ignorant in significant figures. hope that helps:)
Answer:
Some of the calcium carbonate remained stuck to the side of the glassware after filtering
Some of the calcium carbonate spilled when measuring its mass
Explanation:
The percent yield is obtained from;
Actual yield/Theoretical yield * 100
Usually, the actual yield is less than the theoretical yield thereby making the percent yield less than 100%.
In the case of this particular reaction; when some calcium carbonate remains stuck on the glassware or some calcium carbonate is spilled during weighing, the actual yield of product obtained from the reaction becomes less than the theoretical or calculated yield hence the percent yield becomes less than 100%.
