Magnesium metal reacts with phosphoric acid to produce hydrogen gas. If 50 g of phosphoric acid is used, how much magnesium metal is needed? How much hydrogen gas is produced?
To determine how much magnesium metal is needed, we need to know the balanced chemical equation for the reaction between magnesium and phosphoric acid.
The balanced chemical equation is:
3 Mg + 2 H3PO4 -> 3 Mg(PO4)2 + 3 H2
From the balanced equation, we can see that 3 moles of magnesium react with 2 moles of phosphoric acid to produce 3 moles of hydrogen gas.
Now, we need to calculate the molar mass of phosphoric acid (H3PO4) and use stoichiometry to find the amount of magnesium needed.
1. Calculate the molar mass of phosphoric acid (H3PO4):
- Molar mass of H = 1 g/mol
- Molar mass of P = 31 g/mol
- Molar mass of O = 16 g/mol
Total molar mass of H3PO4 = (3 * 1 g/mol) + 31 g/mol + (4 * 16 g/mol) = 98 g/mol
2. Determine the number of moles of phosphoric acid:
Given mass of phosphoric acid = 50 g
Number of moles = Mass / Molar mass = 50 g / 98 g/mol ≈ 0.51 mol
3. Use stoichiometry to find the amount of magnesium needed:
From the balanced equation, we know that 2 moles of phosphoric acid react with 3 moles of magnesium.
Therefore, the number of moles of magnesium needed = (3 moles / 2 moles) * 0.51 mol ≈ 0.77 mol
4. Calculate the mass of magnesium needed:
Molar mass of magnesium = 24 g/mol (approximately)
Mass of magnesium = Number of moles * Molar mass = 0.77 mol * 24 g/mol ≈ 18.5 g
Therefore, approximately 18.5 grams of magnesium metal is needed.
5. Calculate the amount of hydrogen gas produced:
From the balanced equation, we know that 3 moles of magnesium produce 3 moles of hydrogen gas.
Therefore, the number of moles of hydrogen gas produced = 0.51 mol
To calculate the mass of hydrogen gas, we need to know its molar mass:
- Molar mass of H2 = 2 g/mol
Mass of hydrogen gas = Number of moles * Molar mass = 0.51 mol * 2 g/mol = 1.02 g
Therefore, approximately 1.02 grams of hydrogen gas is produced.
To solve this problem, we need to use the balanced chemical equation for the reaction between magnesium metal (Mg) and phosphoric acid (H3PO4):
3Mg + 2H3PO4 → 3MgPO4 + 3H2
From the equation, we can see that for every 2 moles of phosphoric acid (H3PO4), we need 3 moles of magnesium (3Mg). Now, let's calculate the amount of magnesium metal needed.
Step 1: Calculate the molar mass of phosphoric acid.
Given that the molar masses are:
H = 1 g/mol
P = 31 g/mol
O = 16 g/mol
Molar mass of H3PO4 = (3 * 1) + (1 * 31) + (4 * 16) = 3 + 31 + 64 = 98 g/mol
Step 2: Convert the given mass of phosphoric acid to moles.
Using the equation: Moles = Mass / Molar mass
Moles of H3PO4 = 50 g / 98 g/mol ≈ 0.51 mol
Step 3: Determine the stoichiometric ratio.
From the balanced equation, we can see that the stoichiometric ratio between H3PO4 and Mg is 2:3. This means that for every 2 moles of H3PO4, we need 3 moles of Mg.
Step 4: Calculate the moles of Mg required.
Moles of Mg = (Moles of H3PO4 / 2) * 3
Moles of Mg = (0.51 mol / 2) * 3 ≈ 0.77 mol
Step 5: Convert moles of Mg to grams.
Using the molar mass of Mg (24 g/mol), we can calculate the grams of Mg required.
Mass of Mg = Moles of Mg * Molar mass of Mg
Mass of Mg = 0.77 mol * 24 g/mol ≈ 18.48 g
Therefore, approximately 18.48 grams of magnesium metal is needed for the reaction.
Now, let's calculate the amount of hydrogen gas produced.
Step 1: Determine the stoichiometric ratio.
From the balanced equation, we can see that the stoichiometric ratio between Mg and H2 is 3:3. This means that for every 3 moles of Mg, we produce 3 moles of H2.
Step 2: Calculate the moles of H2 produced.
Moles of H2 = (Moles of Mg / 3) * 3
Moles of H2 = (0.77 mol / 3) * 3 ≈ 0.77 mol
Step 3: Convert moles of H2 to grams.
Using the molar mass of H2 (2 g/mol), we can calculate the grams of H2 produced.
Mass of H2 = Moles of H2 * Molar mass of H2
Mass of H2 = 0.77 mol * 2 g/mol ≈ 1.54 g
Therefore, approximately 1.54 grams of hydrogen gas is produced in the reaction.
3Mg + 2H3PO4 ==> 3H2 + Mg3(PO4)2
mols H3PO4 = grams/molar mass.
Using the coefficients in the balanced equation, convert mols H3PO4 to mols Mg.
Then convert mols Mg to grams. g = mols Mg x atomic mass Mg.