Answer:
0.257M HNO3
Explanation:
The reaction of HNO3 with Ba(OH)2 is:
2 HNO₃ + Ba(OH)₂ → 2 H₂O + Ba(NO₃)₂
That means 2 moles of HNO3 reacts with 1 mole of Ba(OH)2.
51,3mL of 0.250M Ba(OH)2 are:
0.0513L ₓ (0.250mol / L) = 0.0128moles
Moles of HNO3 are:
0.0128moles Ba(OH)2 ₓ (2 mol HNO3 / 1 mol Ba(OH)2) = 0.0257mol HNO3
As these moles are in 0.100L:
0.0257mol HNO3 / 0.100L = <em>0.257M HNO3</em>
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I hope it helps!