I was given the following problem:
what is the normality of a solution containing 6 grams of H2SO4 in a 200ml solution? my teacher obtained a normality of 39normals while I took into account that I had two hydrogen free and obtained a result of 0.6 N, who's right?
.6 is correct ... due to H⁺ activity
Did you make a typo and you meant to type in that the teacher obtained 0.30 N?
Technically, you can't say. Both could be right but I disagree with Scott as to why that is so. You must know the equation involved. For example, if you titrate one(1) H then
mL x N x milliequivalent weight = grams.
200 x N x 0.098 = 6g and N = 0.31 which rounds to 0.3 N to 1 sig fig. and the equation is
NaOH + H2SO4 ==> NaHSO4 + H2O
BUT
if the equation is
2NaOH + H2SO4 ==> Na2SO4 + 2H2O then
200 x N x 0.049 = 6 and N = 0.61 which rounds to 0.6 to 1 s.f.
The equivalent weight of H2SO4 is 98 when 1 H is used but it is 98/2 = 40 when both H atoms are used.
To determine who is right, let's first understand what normality is and how it is calculated.
Normality (N) is a unit of concentration used in acid-base chemistry, particularly for solutions that can donate or accept multiple protons (such as sulfuric acid, H2SO4). It represents the number of acid or base equivalents per liter of solution.
To calculate normality, we need to calculate the number of acid or base equivalents present in the given solution. For sulfuric acid (H2SO4), each molecule can donate two acidic hydrogen ions (equivalents).
Given that you have 6 grams of H2SO4 in a 200 ml solution, we need to convert the mass of the acid to moles, then calculate the number of equivalents.
1. Calculate the molar mass of sulfuric acid (H2SO4):
H2: 2(1.008 g/mol) = 2.016 g/mol
S: 32.07 g/mol
O4: 4(16.00 g/mol) = 64.00 g/mol
Total molar mass of H2SO4 = 2.016 + 32.07 + 64.00 = 98.086 g/mol (approximately)
2. Calculate the number of moles of H2SO4 in the given 6 grams:
Moles = Mass / Molar mass
Moles = 6 g / 98.086 g/mol ≈ 0.0612 mol
3. Determine the number of equivalents of H2SO4:
Since each H2SO4 molecule can donate two acidic hydrogen ions (equivalents), we multiply the moles by 2:
Equivalents = Moles × 2 = 0.0612 mol × 2 = 0.1224 eq
Now, let's explore the two answers you and your teacher obtained:
- Your calculation of normality:
Normality (N) = Equivalents / Volume (in liters)
= 0.1224 eq / 0.2 L
= 0.612 N
- Your teacher's calculation of normality:
Normality (N) = 39 N
Based on the calculations, it seems that your teacher's result of 39 N is highly unlikely. It is possible that a mistake was made in their calculation.
Therefore, your answer of 0.612 N is likely the correct one.
It's always essential to double-check calculations and make sure all the steps are followed correctly. In this case, it seems that you accounted for the number of acidic hydrogen ions correctly, resulting in a more accurate normality value.