Question

1. What mass of H2O will be produced if 9.5 g of H2 reacts with 1.2 g of O2?

__ H2 + __ O2 --> __ H2O

2. If 1.85 g of Mg(OH)2 reacts with 3.71 g of HCl, how much MgCl2 is produced? What is the limiting reactant?

__ Mg(OH)2 + __ HCl --> __ MgCl2 + __ H2O

3. What mass of potassium hydroxide is formed when 8.2 g of potassium oxide is added to 1.3 g of water?

__ K2O + __ H2O --> __ KOH

4. What mass of aluminum chloride could be made from 8.1 g of aluminum and 4.2 L of chlorine at STP?

__ Al + __ Cl2 --> __ AlCl3


I know this is a lot of questions but please help and show your work. Thank you.

Answer 1

This is the number 3..

Answer 2

1) The answer is: mass of water is 1.35 grams.

Balanced chemical reaction: 2H₂ + O₂ → 2H₂O.

m(O₂) = 1.2 g; mass of oxygen.

M(O₂) = 2 · 16 g/mol.

M = 32 g/mol, molar mass of oxygen.

n(O₂) = m(O₂) ÷ M(O₂).

n(O₂) = 1.2 g ÷ 32 g/mol.

n(O₂) = 0.0375 mol; amount of oxygen, limiting reactant.

m(H₂) = 9.5 g; mass of hydrogen.

M(H₂) = 2 g/mol, molar mass of hydrogen.

n(H₂) = m(H₂) ÷ M(H₂).

n(H₂) = 9.5 g ÷ 2 g/mol.

n(H₂) = 4.5 mol; amount of hydrogen.

From chemical reaction: n(O₂) : n(H₂O) = 1 : 2.

n(H₂O) = 0.0375 mol · 2.

n(H₂O) = 0.075 mol; amount of water.

m(H₂O) = n(H₂O) · M(H₂O).

m(H₂O) = 0.075 mol · 18 g/mol.

m(H₂O) = 1.35 g; mass of water.

2) The answer is: 3.05 grams of MgCl₂ is produced, the limiting reactant is Mg(OH)₂.

Balanced chemical reaction: 2HCl + Mg(OH)₂ → MgCl₂ + 2H₂O.

m(Mg(OH)₂) = 1.85 g; mass of magnesium hydroxide

n(Mg(OH)₂) = m(Mg(OH)₂) ÷ M(Mg(OH)₂).

n(Mg(OH)₂) = 1.85 g ÷ 58.32 g/mol.

n(Mg(OH)₂) = 0.032 mol; limiting reactant.

m(HCl) = 3.71 g; mass of hydrochloric acid.

n(HCl) = 3.71 g ÷ 36.46 g/mol.

n(HCl) = 0.102 mol; amount of hydrochloric acid.

From chemical reaction: n(Mg(OH)₂) : n(MgCl₂) = 1 : 1.

n(MgCl₂) =0.032 mol; amount of magnesium chloride.

m(MgCl₂) = n(MgCl₂) · M(MgCl₂).

m(MgCl₂) = 0.032 mol · 95.21 g/mol.

m(MgCl₂) = 3.05 g; mass of magnesium chloride.

3) The answer is: mass of potassium hydroxide is 8.1 grams.

Balanced chemical reaction: K₂O + H₂O → 2KOH.

m(K₂O) = 8.2 g; mass of potassium oxide.

n(K₂O) = m(K₂O) ÷ M(K₂O).

n(K₂O) = 8.2 g ÷ 94.2 g/mol.

n(K₂O) = 0.087 mol; amount of potassium oxide.

m(H₂O) = 1.3 g; mass of water.

n(H₂O) = 1.3 g ÷ 18 g/mol.

n(H₂O) = 0.072 mol; limiting reactant.

From chemical reaction: n(H₂O) : n(KOH) = 1 : 2.

n(KOH) = 2 · 0.072 mol.

n(KOH) = 0.144 mol.

m(KOH) = 0.144 mol · 56.1 g/mol.

m(KOH) = 8.1 g; mass of potassium hydroxide.

4) The answer is: mass of aluminum chloride is 16.66 grams.

Balanced chemical reaction: 2Al + 3Cl₂ → 2AlCl₃.

m(Al) = 8.1 g; mass of aluminium.

n(Al) = m(Al) ÷ M(Al).

n(Al) = 8.1 g ÷ 27 g/mol.

n(Al) = 0.3 mol.

V(Cl₂) = 4.2 L; volume of chlorine.

n(Cl₂) = 4.2 L ÷ 22.4 L/mol.

n(Cl₂) = 0.1875 mol; limiting reactant.

From chemical reaction: n(Cl₂) : n(AlCl₃) = 3 : 2.

n(AlCl₃) = 2 · 0.1875 mol ÷ 3.

n(AlCl₃) = 0.125 mol; amount of aluminium chloride.

m(AlCl₃) = 0.125 mol · 133.34 g/mol.

m(AlCl₃) = 16.66 g; mass of aluminium chloride.