A 0.286g sample of Zn was used to produce H2(g)by the reaction.
Zn(s)+ 2HCl(aq)> ZnCl2(aq) + H2(g)
The barometric pressure was recorded as 761.6mm Hg and room temperature was 20degreesC. When the water levels of the eudiometer tube and graduated cylinder were equal, the volume of H2 was measured as 94.8mL. Calculate the number of moles of hydrogen gas produced in the reaction. Also, calculate the theoretical number of moles that can be obtained with the given amount of metal. (assume the acid is in excess) Finally, determine the error
1. Use PV = nRT and solve for n = number of mols H2.
P = (761.8- vapor pressure H2O @ 20C)/760 = atm.
V = 0.0948 L
R = 0.08206 L*atm/mol*K
T = 273 + 20 = ?
2.mols Zn = grams/molar mass
Convert mols Zn to mols H2 using the coefficients in the balanced equation. That's mols H2 = mols Zn = theoretical mols H2 produced.
3. T = theoretical value.
E = experimental value.
%error = [(E-T)/T]*100
To calculate the number of moles of hydrogen gas produced in the reaction, we need to use the ideal gas law equation, which is:
PV = nRT
Where:
P is the pressure (in atm),
V is the volume (in liters),
n is the number of moles,
R is the ideal gas constant (0.0821 L·atm/mol·K),
T is the temperature (in Kelvin).
First, we need to convert the given barometric pressure in mm Hg to atm. Since 1 atm is approximately equal to 760 mm Hg, we can use the following conversion factor:
1 atm = 760 mm Hg
So, the barometric pressure in atm is calculated as:
P = 761.6 mm Hg / 760 mm Hg = 1.001 atm
Next, we need to convert the measured volume of H2 gas from milliliters (mL) to liters (L). Since 1 L is equal to 1000 mL, we can use the following conversion factor:
1 L = 1000 mL
The volume in liters is calculated as:
V = 94.8 mL / 1000 mL/L = 0.0948 L
Now, we can rearrange the ideal gas law equation to solve for the number of moles (n):
n = PV / RT
Substituting the values into the equation:
n = (1.001 atm) * (0.0948 L) / (0.0821 L·atm/mol·K) * (20°C + 273.15) K
n = 0.12033 mol
Therefore, the number of moles of hydrogen gas produced in the reaction is approximately 0.12033 mol.
To calculate the theoretical number of moles that can be obtained with the given amount of metal, we need to convert the mass of the Zn sample to moles. The molar mass of Zn is 65.38 g/mol. We can use the following conversion factor:
1 mol Zn = 65.38 g Zn
The mass in grams is calculated as:
m = 0.286 g
n_Zn = m / M_Zn
n_Zn = 0.286 g / 65.38 g/mol
n_Zn = 0.004375 mol
Therefore, the theoretical number of moles of H2 that can be obtained with the given amount of metal is approximately 0.004375 mol.
To determine the error, we can calculate the percent error using the formula:
percent error = |experimental value - theoretical value| / theoretical value * 100%
Substituting the values:
percent error = |0.12033 mol - 0.004375 mol| / 0.004375 mol * 100%
percent error = 2640.23%
Therefore, the error in this case is approximately 2640.23%.