Question

problems

1. $ce{n_{2} + 3h_{2} -> 2nh_{3}}$

how many moles of hydrogen are needed to completely react with two moles of nitrogen?

1. $ce{2kclo_{3} -> 2kcl + 3o_{2}}$

how many moles of oxygen are produced by the decomposition of six moles of potassium chlorate?

1. $ce{zn + 2hcl -> zncl_{2} + h_{2}}$

how many moles of hydrogen are produced from the reaction of three moles of zinc with an excess of hydrochloric acid?

1. $ce{c_{3}h_{8} + 5o_{2} -> 3co_{2} + 4h_{2}o}$

how many moles of oxygen are necessary to react completely with four moles of propane ($ce{c_{3}h_{8}}$)?

1. $ce{k_{3}po_{4} + al(no_{3})_{3} -> 3kno_{3} + alpo_{4}}$

how many moles of potassium nitrate are produced when two moles of potassium phosphate react with two moles of aluminum nitrate?

Explanation:

Step1: Use mole ratio for N₂/H₂

From $\ce{N2 + 3H2 -> 2NH3}$, mole ratio $\frac{n(\ce{H2})}{n(\ce{N2})}=\frac{3}{1}$.
$n(\ce{H2}) = 3 \times n(\ce{N2}) = 3 \times 2 = 6$ moles

Step2: Use mole ratio for KClO₃/O₂

From $\ce{2KClO3 -> 2KCl + 3O2}$, mole ratio $\frac{n(\ce{O2})}{n(\ce{KClO3})}=\frac{3}{2}$.
$n(\ce{O2}) = \frac{3}{2} \times n(\ce{KClO3}) = \frac{3}{2} \times 6 = 9$ moles

Step3: Use mole ratio for Zn/H₂

From $\ce{Zn + 2HCl -> ZnCl2 + H2}$, mole ratio $\frac{n(\ce{H2})}{n(\ce{Zn})}=\frac{1}{1}$.
$n(\ce{H2}) = 1 \times n(\ce{Zn}) = 1 \times 3 = 3$ moles

Step4: Use mole ratio for C₃H₈/O₂

From $\ce{C3H8 + 5O2 -> 3CO2 + 4H2O}$, mole ratio $\frac{n(\ce{O2})}{n(\ce{C3H8})}=\frac{5}{1}$.
$n(\ce{O2}) = 5 \times n(\ce{C3H8}) = 5 \times 4 = 20$ moles

Step5: Identify limiting reactant, use ratio

From $\ce{K3PO4 + Al(NO3)3 -> 3KNO3 + AlPO4}$, mole ratio $\frac{n(\ce{K3PO4})}{n(\ce{Al(NO3)3})}=\frac{1}{1}$. 2 moles of each react, so no excess. Ratio $\frac{n(\ce{KNO3})}{n(\ce{K3PO4})}=\frac{3}{1}$.
$n(\ce{KNO3}) = 3 \times n(\ce{K3PO4}) = 3 \times 2 = 6$ moles

Answer:

1. 6 moles
2. 9 moles
3. 3 moles
4. 20 moles
5. 6 moles