Question

How many moles of H, O are required to form 1.4 L of O2 at a temperature of 323 K and a pressure of 0.993 atm?Express your answer using two significant figures.

Answer 1

We have the decomposition reaction of water that is described by the following balanced equation:

`2H_2O\rightarrow2H_2+O_2`

To solve the question we will follow the following steps.

1. We find the moles of O2 formed from the ideal gas law that tells us:

`PV=nRT`

Where,

P is the pressure of the gas, 0.993atm

V is the volume of the gas, 1.4L

T is the temperature of the gas, 323K

R is a constant, 0.08206atm-L/mol.K

n is the number of moles

We clear the number of moles and replace the known data:

`\begin{gathered} n=(PV)/(RT) \\ n=(0.993atm*1.4L)/(0.08206(atm.L)/(mol.K)*323K)=0.052molO_2 \end{gathered}`

2. We find the moles of H2O needed from the stoichiometry of the reaction. Two moles of water produce one mol of O2, so the ratio H2O to O2 is 2/1.

`\begin{gathered} MolH_2O=0.052molO_2*(2molH_2O)/(1molO_2) \\ MolH_2O=0.10molH_2O \end{gathered}`

Answer: Are required 0.10mol of H2O