Iron is attacked by acids when an iron nail of mass m = 1.5 g is placed in
a volume V = 10mL of a hydrochloric acid solution (H* + CI-) of concentration
C = 0.8mol. L-1
, we observe a gaseous release of dihydrogen (H2) and femmation
of iron II ions (Fe?+).
© Write the balance equation for the reaction and indicate the torques involved.
® Take stock of the species present in the initial state.
• Has the nail been completely destroyed?
© Accurately indicate the quantities of materials present in the solution when the reaction is complete.
© What is the volume of hydrogen released by this reaction?
What is the concentration of iron II ions and H+ ions when the reaction is complete?
Data
: "The molar volume under the experimental conditions: V M = 24L/mol
• The molar mass of iron: M (Fe) = 55.8g/mol
The balanced equation for the reaction between iron and hydrochloric acid can be written as:
Fe(s) + 2HCl(aq) → FeCl2(aq) + H2(g)
The torques involved in this reaction are the release of dihydrogen gas and the formation of iron II ions.
In the initial state, we have a 1.5 g iron nail and a volume of 10 mL hydrochloric acid solution with a concentration of 0.8 mol/L. The species present are iron (Fe), hydrochloric acid (HCl), hydrogen ions (H+), and chloride ions (Cl-).
The nail may not be completely destroyed, but it will react with the hydrochloric acid to form iron II ions and release dihydrogen gas.
To determine the quantities of materials present in the solution when the reaction is complete, we need to use the mole ratios from the balanced equation.
From the balanced equation, we can see that 1 mole of iron reacts with 2 moles of hydrochloric acid to produce 1 mole of iron II ions and 1 mole of dihydrogen gas.
Using the given molar mass of iron (55.8 g/mol), we can calculate the number of moles of iron present:
Number of moles of iron = mass / molar mass = 1.5 g / 55.8 g/mol ≈ 0.0269 mol
Since the mole ratio between iron and hydrochloric acid is 1:2, the number of moles of hydrochloric acid consumed is twice the number of moles of iron:
Number of moles of HCl consumed = 2 * number of moles of iron = 2 * 0.0269 mol = 0.0538 mol
Using the given concentration of hydrochloric acid (0.8 mol/L) and the volume of solution (10 mL), we can calculate the number of moles of HCl present:
Number of moles of HCl = concentration * volume = 0.8 mol/L * 0.01 L = 0.008 mol
Therefore, the remaining moles of HCl after the reaction is complete are:
Remaining moles of HCl = initial moles of HCl - moles of HCl consumed = 0.008 mol - 0.0538 mol = -0.0458 mol
Since the reaction is complete, all of the hydrochloric acid is consumed, and the final amount of HCl becomes 0 moles.
The volume of hydrogen released by this reaction can be calculated by using the molar volume under the experimental conditions:
Volume of hydrogen = moles of H2 * molar volume = 0.0269 mol * 24 L/mol = 0.6464 L or 646.4 mL
When the reaction is complete, all of the iron is converted into iron II ions (Fe2+). Since the initial volume of the solution is 10 mL and the concentration of iron II ions is not given, we do not have enough information to determine the concentration of iron II ions when the reaction is complete.
Similarly, since the concentration of H+ ions is not given, we do not have enough information to determine the concentration of H+ ions when the reaction is complete.
Balance equation for the reaction:
Fe + 2HCl → FeCl2 + H2
Species present in the initial state:
- Iron (Fe) as a solid nail
- Hydrochloric acid (HCl) in solution
- Chloride ions (Cl-) in solution
- Hydrogen ions (H+) in solution
Whether the nail has been completely destroyed depends on the extent of the reaction. Assuming the reaction is complete, the nail would have been completely reacted.
Quantities of materials present in the solution when the reaction is complete:
- Iron (Fe) has reacted completely
- Hydrochloric acid (HCl) will have undergone reaction with the iron, hence the concentration would decrease
- Iron II ions (Fe2+) and chloride ions (Cl-) will be present in the solution
Volume of hydrogen released by this reaction:
To determine the volume of hydrogen released, we need to use the ideal gas law equation: PV = nRT
Given:
- Molar volume under experimental conditions: VM = 24 L/mol
- Molar mass of iron: M(Fe) = 55.8 g/mol
- Mass of iron nail: m = 1.5 g
First, calculate the number of moles of iron:
n(Fe) = m/M(Fe) = 1.5 g / 55.8 g/mol ≈ 0.0269 mol
Since the reaction stoichiometry indicates that 1 mole of iron reacts to produce 1 mole of hydrogen, the volume of hydrogen released will be equal to the number of moles of hydrogen produced (assuming ideal gas behavior).
V(H2) = n(H2) x VM = 0.0269 mol x 24 L/mol ≈ 0.646 L
Concentration of iron II ions (Fe2+) and hydrogen ions (H+) when the reaction is complete:
Since the reaction has gone to completion, all the iron has reacted to form iron II ions (Fe2+). The concentration of Fe2+ ions in the solution will depend on the final volume of the solution.
Using the given volume of hydrochloric acid solution (V = 10 mL = 10 cm^3),
C(Fe2+) = n(Fe2+) / V = 0.0269 mol / 0.01 L = 2.69 mol/L
Similarly, the concentration of H+ ions will be the same as the initial concentration of HCl, which is given as C = 0.8 mol/L.
To answer the questions:
1. The balanced equation for the reaction is:
Fe(s) + 2HCl(aq) → FeCl2(aq) + H2(g)
2. The species present in the initial state are the iron nail (Fe(s)), hydrochloric acid (HCl(aq)), and chloride ions (Cl-) from the dissociation of HCl.
3. Whether the nail is completely destroyed depends on the amount of reactants and the reaction conditions. However, based on the given information, we cannot determine if the nail is completely destroyed.
4. When the reaction is complete, all of the hydrochloric acid will be consumed, and the only species left in the solution will be iron II ions (Fe2+) from the formation of iron II chloride (FeCl2).
5. To find the volume of hydrogen released, we need to use the molar ratios from the balanced equation. From the balanced equation, we see that 1 mole of iron reacts with 2 moles of hydrochloric acid to form 1 mole of hydrogen.
Given that the concentration of HCl is 0.8 mol/L and the volume of the solution is 10 mL (which is equivalent to 0.01 L), we can calculate the amount of HCl reacted:
Amount of HCl = concentration × volume = 0.8 mol/L × 0.01 L = 0.008 mol
Since 1 mole of iron reacts with 2 moles of HCl to produce 1 mole of hydrogen gas, the amount of hydrogen released will be half of the amount of HCl reacted:
Amount of H2 = 0.008 mol / 2 = 0.004 mol
To calculate the volume of hydrogen gas released, we use the molar volume of a gas at the given experimental conditions:
Volume of H2 = Amount of H2 × Molar volume = 0.004 mol × 24 L/mol = 0.096 L or 96 mL
Therefore, the volume of hydrogen gas released by this reaction is 0.096 L or 96 mL.
6. The concentration of iron II ions (Fe2+) is equal to the amount of FeCl2 formed divided by the final volume of the solution. Given that the reaction is complete and the only species left in the solution is FeCl2, we can calculate the concentration:
Amount of FeCl2 = Amount of Fe reacted = mass of iron nail / molar mass of iron
Amount of FeCl2 = 1.5 g / 55.8 g/mol ≈ 0.02684 mol
Final volume of solution = initial volume of solution = 10 mL = 0.01 L
Concentration of Fe2+ = Amount of FeCl2 / Final volume of solution
Concentration of Fe2+ = 0.02684 mol / 0.01 L = 2.68 mol/L
Therefore, when the reaction is complete, the concentration of iron II ions is 2.68 mol/L.
Since the reaction produces 2 moles of H+ ions for every mole of HCl consumed, the concentration of H+ ions will be twice the initial concentration of HCl:
Concentration of H+ = 2 × Concentration of HCl = 2 × 0.8 mol/L = 1.6 mol/L
Therefore, when the reaction is complete, the concentration of H+ ions is 1.6 mol/L.