You place 2.80 g of phosphoric acid (H3PO4) into 150.0ml of a 1.00M sodium hydroxide solution. If the total volume remains constant, determine the following

Question

(Hint: this is an acid base reaction)

 

1. the concentration of sodium ion at the completion of the reaction____

2. the concentration of phosphate ion at the completion of the reaction____

3. the concentration of hydroxide ion at the completion of the reaction_____

Answer 1

Balanced equation:

3NaOH + H3PO4 ==> Na3PO4 + 3H2O

moles NaOH = 0.15 L x 1.00 mol/L = 0.150 moles

moles H3PO4 = 2.80 g x 1 mol/97.99 g = 0.0286 mol

1.  [Na] = 0.150 mol/0.150L = 1.00 M

2.  [PO4] = 0.0286 mol/0.150L = 0.191 M

3.  [OH] = 0.15 mol - (3x0.0286 mol)=0.0642 mol

0.0642 mol/0.15L = 0.428 M