Question

Iron reacts with dilute HCL to produce hydrogen gas and iron 2 chloride. What volume of dry hydrogen, measured at 22 Celsius and 750 mmHg (room pressure) would be evolved from reacting 0.8827g of iron with an excess amount of HCL?

Answer 1

You first need to write and balance the reaction for whats happening.
Then convert the mass given of Iron to moles.
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To convert mass to moles, use the relationship:

\(n=\dfrac{m}{M}\)

where, M=molar mass, m=mass, and n= moles.

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Since the other reactant is in excess, the limiting reactant is Iron. So use the moles of iron for find the moles of \(H_{2~ (g)}\) produced using the stoichiometric coefficients. Set up a ratio using the species of interest, like so:

e.g. for a general reaction:

\(\color{red}{a}A + \color{blue}{b}B\) \(\rightleftharpoons\) \( \color{green}{c}C\)

where upper case are the species (A,B,C), and lower case (a,b,c) are the coefficients ,

\(\dfrac{n_A}{\color{red}{a}}=\dfrac{n_B}{\color{blue}{b}}=\dfrac{n_C}{\color{green}{c}}\)

From here you can isolate what you need.
For example: if you have 2 moles of B, how many moles of C can you produce?

solve algebraically: \(\dfrac{2}{\color{blue}{b}}=\dfrac{n_C}{\color{green}{c}}\rightarrow n_C=\dfrac{2*\color{green}{c}}{\color{blue}{b}}\)
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Finally, use moles found of hydrogen gas and the ideal gas formula: PV=nRT

Solve for volume.