# Finding partial pressure of a gas in a mixture

A mixture of argon and carbon dioxide was initially at a total pressure of $\pu{1.72 atm}$ in a volume of $\pu{1.72 L}$ at $\pu{17 ^\circ C}$. The carbon dioxide was then completely removed from the mixture by passing it through a solution of sodium hydroxide ($\ce{NaOH}$). The argon was collected in a $\pu{1.1 L}$ vessel and its pressure found to be $\pu{1.55 atm}$ at a temperature of $\pu{28 ^\circ C}$. What was the partial pressure of carbon dioxide in the original gas mixture? Assume that argon and carbon dioxide behave as ideal gases.

So, initially I found the moles of argon in in a $\pu{1.1 L}$ vessel which is $\pu{0.06896 moles}$

Then, i subtracted $\pu{1.72 L}$ from $\pu{1.1 L}$ in order to get a volume of carbon dioxide and used it in $PV = nRT$ and i got $\pu{0.04474 moles}$ of carbon dioxide .

Finally, I used the formula for partial pressure

$\frac{\text{moles of carbon dioxide} \times\text{total pressure}}{\text{moles of argon} + \text{moles of carbon dioxide}}$ and got $\pu{0.6771 atm}$.

However, my answer is not correct according to the textbook. Where did i make a mistake?