J.R. S. answered 04/08/20
Ph.D. University Professor with 10+ years Tutoring Experience
KOH + HNO3 ==> H2O + KNO3
(28.6 ml)(0.207 M) = (x ml)(0.143 M)
x = 41.4 ml
Done another way;
moles KOH present = 0.0286 L x 0.207 mol/L = 0.00592 moles. This is also moles of HNO3 needed
(x L)(0.143 mol/L) = 0.00592 moles HNO3
x = 0.0414 L = 41.4 mls