Answer:
4.8 grams
Explanation:
Use PV=nRT
P: 775 mmHg (divide by 760 mmHg to get atm) -> 1.02 atm
V: 3700 mL (divide by 1000 to get L) -> 3.7L
n: ?
R: (a constant) 0.0821L * atm/k *mol
T: 33 C (add 273 to get K) -> 306K
Move equation so n is on the side: PV/RT = n. Plug the numbers into the equation.
Then, convert moles to grams using the molar mass of O2 which is 32g/mol.
= 4.8g
This problem is describing the equilibrium whereby hydrofluoric acid decomposes to hydrogen and fluorine gases at 298 K whose equilibrium constant is 8.70x10⁻³, the equilibrium concentrations of all the reactants are both 1.33x10⁻³ M and asks for the initial concentration of hydrofluoric acid which turns out to be 2.86x10⁻³ M.
Then, we can write the following equilibrium expression for hydrofluoric acid once the change, , has taken place:
Now, since both products are 1.33x10⁻³ M we infer the reaction extent is also 1.33x10⁻³ M, and thus, we can calculate the equilibrium concentration of HF via the law of mass action (equilibrium expression):
Finally, the initial concentration of HF is calculated as follows:
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