A certain amount of calcium reacts with water and the formed hydroxide 49g completely neutralized phosphoric acid. Calculate the volume of hydrogen obtained,
at STP, and the mass of calcium.
Ca + 2H2O ==> Ca(OH)2 + H2
mols Ca(OH)2 = grams/molar mass = ?
Using the coefficients in the balanced equation, convert mols Ca(OH)2 to mols H2.
Then use PV = nRT OR 1 mol at STP is 22.4L to convert to volume.
For grams Ca, g = mols x molar mass.
thank you so much DrBob222 ^^
To calculate the volume of hydrogen obtained, we need to first determine the number of moles of phosphoric acid that was neutralized. We can then use the stoichiometry of the balanced chemical equation to find the number of moles of hydrogen gas produced.
1. Determine the number of moles of phosphoric acid:
We know that the hydroxide completely neutralized the phosphoric acid. The molar mass of phosphoric acid (H₃PO₄) is 98 g/mol. Therefore, the number of moles of phosphoric acid is:
Moles of phosphoric acid = mass of phosphoric acid / molar mass of phosphoric acid
Given that 49 g of phosphoric acid was neutralized:
Moles of phosphoric acid = 49 g / 98 g/mol = 0.5 mol
2. Use the stoichiometry of the balanced chemical equation:
The balanced chemical equation for the reaction of calcium with water is:
Ca + 2H₂O → Ca(OH)₂ + H₂
From the equation, we can see that one mole of calcium reacts with one mole of hydrogen gas. Therefore, the number of moles of hydrogen gas produced is also 0.5 mol.
3. Calculate the volume of hydrogen gas using the ideal gas law:
At STP (Standard Temperature and Pressure), one mole of any gas occupies 22.4 L of volume. Therefore, since we have 0.5 moles of hydrogen gas, the volume can be calculated as:
Volume of hydrogen gas = 0.5 mol * 22.4 L/mol = 11.2 L
So, the volume of hydrogen gas obtained is 11.2 liters at STP.
To calculate the mass of calcium that reacted, we can use the stoichiometry of the balanced chemical equation again:
From the balanced equation, we can see that 1 mole of calcium reacts to produce 1 mole of hydrogen gas. Therefore, the number of moles of calcium is also 0.5 mol.
Finally, to find the mass of calcium that reacted, we need to multiply the number of moles of calcium with its molar mass:
Mass of calcium = moles of calcium * molar mass of calcium
Assuming the molar mass of calcium is 40 g/mol:
Mass of calcium = 0.5 mol * 40 g/mol = 20 g
So, the mass of calcium that reacted is 20 grams.