# Determine the mass of Н3РО4 in the solution, if when titrating it with methyl orange there is 25.50 cm3 of a 0.2000 M NaOH solution Decision:
M (H3PO4) = 98 g / mol.
The reaction equation has the form:
Н3РО4 + 3NaOH = Na3PO4 + 3H2O
From the equation it follows that titration of 1 mol of Н3РО4 requires 3 mol of NaOH, n (Н3РО4) = 1 / 3n (NaOH).
1) We find the amount of NaOH used for titration:
n (NaOH) = [CM (NaOH). V (NaOH)] / 1000 = (25.5. 0.2000) / 1000 = 0.0051 mol.
2) we find the amount of Н3РО4, we get:
n (H3PO4) = 1 / 3n (NaOH) = 0.0051 / 3 = 0.0017 mol.
3) We find the mass of Н3РО4 in solution, we get:
m (H3PO4) = n (H3PO4). M (H3PO4) = 0.0017. 98 = 0.1666 g.
The problem can be solved in one action, using one formula:
m (H3PO4) = V (p-pa) [NaOH]. CM (NaOH). M (Н3РО4) / (1000. 3) = (25.5. 0.2000. 98) / (1000. 3) = 0.1666 g.
Answer: m (Н3РО4) = 0.1666 g Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.