Question

3.) magnesium reacts with Hydro chloric acid according to the following equation: Mg + 2 HCI —> MgCI2 + H2. If 0.30 mole of Mg reacts how many molecules of HCI Will also react?

Answer 1

There are 3.6x10^23 molecules of HCl that will react.

1st) From the equation we know that 1 mole of Magnesium (Mg) reacts with 2 moles of Hydrochloric acid (HCl), so with a mathematical Rule of Three we can calculate themoles of HCl that will react with 0.30 moles of Mg.

$\begin{gathered} 1\text{molMg}-2\text{molHCl} \\ 0.30\text{molMg}-x=\frac{0.30\text{molMg}\cdot2\text{molHCl}}{1\text{molMg}} \\ \\ x=0.60\text{molHCl} \end{gathered}$

So, 0.60 moles of HCl will react with 0.30 moles of Mg.

2nd) Now we have to calculate the amount of molecules in 0.30 moles of HCl. Here it is necessary to use the Avogadro's number (6.022x10^23 particles):

$\begin{gathered} 1\text{molHCl}-6.022\cdot10^{23}molecules \\ 0.60\text{molHCl}-x=\frac{0.60\text{molHCl}\cdot6.022\cdot10^{23}molecules}{1\text{molHCl}} \\ \\ x=3.6\cdot10^{23}molecules \end{gathered}$

Finally, there are 3.6x10^23 molecules of HCl that will react.