6g of Mg was to 100cm3 of 1 moldm3 H2 SO4 . What mass of Mg remained undissolved? (Mg = 24)
Answer Details
The balanced chemical equation for the reaction between magnesium (Mg) and sulfuric acid (H2SO4) is:
Mg + H2SO4 -> MgSO4 + H2
According to the equation, one mole of Mg reacts with one mole of H2SO4 to produce one mole of magnesium sulfate (MgSO4) and one mole of hydrogen gas (H2). Since the concentration of the sulfuric acid is 1 moldm3, this means that there is one mole of H2SO4 in every 1 liter (1000 cm3) of solution.
To determine the amount of Mg that reacts with the H2SO4, we need to use stoichiometry. One mole of Mg reacts with one mole of H2SO4, so the amount of Mg that reacts with 1 moldm3 of H2SO4 is given by:
6g / 24g/mol = 0.25 mol
Since the reaction is 1:1, this means that 0.25 mol of H2SO4 is consumed in the reaction. The volume of the solution is 100cm3 (0.1 dm3), so the amount of H2SO4 in the solution is:
1 mol/dm3 x 0.1 dm3 = 0.1 mol
The amount of H2SO4 that remains after the reaction is:
0.1 mol - 0.25 mol = -0.15 mol
This negative value means that all of the H2SO4 was consumed in the reaction, and there is excess Mg left over. The mass of Mg that remains undissolved is given by:
0.15 mol x 24g/mol = 3.6g
Therefore, the correct answer is 3.6g.