The volume of a mass of gas is 300 ml at 25°C and 685 torr. What will the gas occupy at STP?
Would the answer be 248 ml?
yes
how can u get 248 though
To find the volume of a gas at STP (Standard Temperature and Pressure), you can use the ideal gas law equation, which states:
PV = nRT
where:
- P represents the pressure,
- V represents the volume,
- n represents the number of moles,
- R is the ideal gas constant (0.0821 L·atm/(mol·K)), and
- T represents the temperature in Kelvin.
To solve the problem, you can follow these steps:
1. Convert the temperature from Celsius to Kelvin:
To convert from Celsius to Kelvin, you need to add 273.15 to the Celsius value.
T(K) = T(°C) + 273.15
T(K) = 25°C + 273.15 = 298.15 K
2. Convert the pressure from torr to atm:
To convert from torr to atm, you need to divide the torr value by 760.
P(atm) = P(torr) / 760
P(atm) = 685 torr / 760 = 0.9013 atm
3. Use the ideal gas law equation to find the number of moles:
Rearranging the equation, we get:
n = (PV) / (RT)
Now plug in the values:
P = 0.9013 atm
V = 300 ml = 0.3 L (since 1 L = 1000 mL)
R = 0.0821 L·atm/(mol·K)
T = 298.15 K
n = (0.9013 atm * 0.3 L) / (0.0821 L·atm/(mol·K) * 298.15 K)
Simplify the equation:
n ≈ 0.0111 mol
4. Determine the volume at STP:
At STP, the pressure is 1 atm and the temperature is 273.15 K.
Now use the ideal gas law again:
V = (nRT) / P
Plug in the values:
n = 0.0111 mol
R = 0.0821 L·atm/(mol·K)
T = 273.15 K
P = 1 atm
V = (0.0111 mol * 0.0821 L·atm/(mol·K) * 273.15 K) / 1 atm
Simplify the equation:
V ≈ 0.246 L
To find the volume in mL, multiply the volume in liters by 1000:
V(mL) = 0.246 L * 1000 = 246 mL
Therefore, the volume of the gas at STP would be approximately 246 mL, not 248 mL.