Describe how you can show that a chemical reaction adhers to the law of conservation of mass. Chemical reaction: magnesium hydroxide added to phosphoric acid produces magnesium phosphate and water. Find the mass percentage of each compound as well as the total mass of reactants compared to the total mass of products
Write the equation and balance it.
3Mg(OH)2 + 2H3PO4 ==>Mg3(PO4)2 + 6H2O
Start with a convenient amount of Mg(OH)2 and H3PO4. I would suggest 3 mol Mg(OH)2 and 2 mols H3PO4. With stoichiometry, determine mols of the salt produced and mols H2O produced. Now describe how you would go about experimentally showing that the mass of the products is th same as the mass of the reactants.
To show that a chemical reaction adheres to the law of conservation of mass, you need to demonstrate that the sum of the masses of the reactants equals the sum of the masses of the products. In this case, you need to find the mass percentage of each compound involved in the reaction and compare the total mass of the reactants to the total mass of the products.
First, let's set up the balanced chemical equation for the reaction you provided:
3Mg(OH)2 + 2H3PO4 → Mg3(PO4)2 + 6H2O
Now, let's calculate the molecular masses of each compound:
Mg(OH)2: 1 magnesium (Mg) atom = 24.31 g/mol, 2 oxygen (O) atoms = 15.999 g/mol each, and 2 hydrogen (H) atoms = 1.008 g/mol each.
Molecular mass of Mg(OH)2 = (24.31 + (2 * 15.999) + (2 * 1.008)) g/mol = 58.32 g/mol.
H3PO4: 3 hydrogen (H) atoms = 1.008 g/mol each, 1 phosphorus (P) atom = 30.97 g/mol, and 4 oxygen (O) atoms = 15.999 g/mol each.
Molecular mass of H3PO4 = ((3 * 1.008) + 30.97 + (4 * 15.999)) g/mol = 98.00 g/mol.
Mg3(PO4)2: 3 magnesium (Mg) atoms = 24.31 g/mol each, 2 phosphorus (P) atoms = 30.97 g/mol each, and 8 oxygen (O) atoms = 15.999 g/mol each.
Molecular mass of Mg3(PO4)2 = ((3 * 24.31) + (2 * 30.97) + (8 * 15.999)) g/mol = 262.86 g/mol.
H2O: 2 hydrogen (H) atoms = 1.008 g/mol each and 1 oxygen (O) atom = 15.999 g/mol.
Molecular mass of H2O = ((2 * 1.008) + 15.999) g/mol = 18.02 g/mol.
Next, let's find the mass percentage of each compound:
Mass percentage of Mg(OH)2 = (mass of Mg(OH)2 / total mass of reactants) * 100
Mass percentage of Mg(OH)2 = (58.32 g/mol / (58.32 g/mol + 98.00 g/mol)) * 100
Mass percentage of Mg(OH)2 ≈ 37.31%
Similarly, you can calculate the mass percentages for the other compounds: H3PO4, Mg3(PO4)2, and H2O.
Finally, to compare the total mass of the reactants to the total mass of the products:
Total mass of reactants = mass of Mg(OH)2 + mass of H3PO4
Total mass of products = mass of Mg3(PO4)2 + mass of H2O
Compare the two values to see if they are approximately equal. If they are, it demonstrates that the law of conservation of mass is upheld in the chemical reaction.