Raoul Pictet, the Swiss physicist who first liquefied oxygen, attempted to liquefy hydrogen. He heated potassium formate, KCHO2, with KOH in a closed 2.50 L vessel.
KCHO2(s) + KOH(s) → K2CO3(s) + H2(g)
If 50.1 g of potassium formate reacts in a 2.50-L vessel, which was initially evacuated, what pressure of hydrogen will be attained when the temperature is finally cooled to 25°C? Use the preceding chemical equation and ignore the volume of solid product.
what equation would you have to use here?
I would try converting KCHO2 to moles. 50.1 g/molar mass = moles, then convert that to M = moles/L (divide moles by 2.5L).
Since 1 mole H2 is formed from 1 mole KCHO2, then use PV = nRT to solve for P. All of the other reactants and products are solids and the problem tells you to ignore the solids.
To solve this problem, we first need to determine the amount of hydrogen gas produced using stoichiometry. Then, we can use the ideal gas law to calculate the pressure of the hydrogen gas.
Let's start by calculating the amount of hydrogen gas produced from the given mass of potassium formate.
1. Calculate the molar mass of potassium formate (KCHO2):
KCHO2 = 39.10 g/mol (K) + 12.01 g/mol (C) + 16.00 g/mol (H) + 32.00 g/mol (O) = 99.11 g/mol
2. Convert the mass of potassium formate to moles:
Moles of KCHO2 = 50.1 g / 99.11 g/mol
3. Use stoichiometry to determine the moles of hydrogen gas produced:
From the balanced chemical equation, we see that 1 mole of KCHO2 produces 1 mole of H2. Therefore, the moles of H2 produced is equal to the moles of KCHO2.
4. Calculate the volume of the hydrogen gas using the ideal gas law:
PV = nRT
P = pressure (to be determined)
V = volume = 2.50 L
n = moles of H2
R = gas constant = 0.0821 L·atm/(mol·K)
T = temperature = 25°C = 298 K (convert to Kelvin)
Rearranging the ideal gas law equation, we have:
P = (nRT) / V
Now we can substitute the known values into the equation and solve for P:
P = (nRT) / V
P = (50.1 g / 99.11 g/mol) * (0.0821 L·atm/(mol·K)) * 298 K / 2.50 L
After simplifying the equation, you should get the pressure of hydrogen gas in atmospheres (atm).