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
Answer:
Explanation:
I'll assume 1.49 is liters.
All gases occupy 22.4 L for each mole of gas at STP. This makles a very useful, and important, conversion factor:
(22.4L/mole gas) for all gases at STP.
Therefore 1.49L of H2 would be:
(1.49L H2)/(22.4L/mole gas) = 0.0665 moles
The molar mass of H2 is 2, so:
(0.0665 moles)*(2g/mole) = 0.133 grams to 3 sig figs
Answer:
5.00g
Explanation:
Molarity is moles per liter
Therefore:
x moles/.250L = .5 moles/1L
Solve for x: .125 moles required
Question asks for grams of NaOH so multiply the moles by the molar mass of NaOH
.125(39.997) = 4.999625g
Rounds to 5.00g
