What is the percentage purity of sample if 3.92g of mohr's salt react completely with 50 ml N/10 Kmno4 solution
To determine the percentage purity of the sample, we need to calculate the number of moles of the substance that reacted and compare it with the theoretical amount. Here's how you can find the answer:
Step 1: Convert the volume of the KMnO4 solution to moles. Since it is a 1 M (N/10) solution, 1 liter of the solution contains 1/10 moles of KMnO4. Therefore, 50 ml of the solution (0.05 liters) contains 0.05 * (1/10) moles.
Step 2: Use the balanced equation of the reaction between Mohr's salt (FeSO4.(NH4)2SO4.6H2O) and KMnO4 to determine the mole ratio between them. The balanced equation is:
5FeSO4.(NH4)2SO4.6H2O + 8KMnO4 + 18H2SO4 → 5Fe2(SO4)3 + 2MnSO4 + 8MnO2 + 8K2SO4 + 18H2O
From the equation, we can see that 8 moles of KMnO4 react with 5 moles of FeSO4.(NH4)2SO4.6H2O.
Step 3: Calculate the moles of FeSO4.(NH4)2SO4.6H2O that reacted. Multiply the moles of KMnO4 from step 1 by the mole ratio between KMnO4 and FeSO4.(NH4)2SO4.6H2O.
For example, if you found 0.05 moles of KMnO4, the number of moles of FeSO4.(NH4)2SO4.6H2O would be 0.05 * (5/8).
Step 4: Convert the moles of FeSO4.(NH4)2SO4.6H2O to grams using the molar mass of the compound. The molar mass of FeSO4.(NH4)2SO4.6H2O can be calculated by summing the atomic masses of its constituents which are Fe, S, O, N, and H.
Step 5: Finally, calculate the percentage purity of the sample. Divide the mass of the sample by the mass of the pure substance, then multiply by 100.
It's important to note that the given mass of Mohr's salt (3.92g) does not provide the exact information about its purity, as there may be impurities present. However, by comparing the expected theoretical mass to the actual mass obtained, we can get an estimate of its purity.
Working in N has real advantages over using M but most schools don't teach that now.
mL x N x milliequivalent weight = g
50 x 0.1 x 0.392 = ?g
(?g/3.92)*100 = % purity.