Question

A is a solution of trioxonitrate(v)acid (nitric acid) HNO3 of unknown concentration.B is a standard solution of sodium hydroxide containing 4.00g per dm3 of solution
a). Suggest with a reason,a suitable indicator for the reaction
b) Write a balanced equation for the reason
c) Calculate
1. The concentration of solution B in moles per dm3
2. The concentration of solution A in moles per dm3
3. The concentration of grams per dm3 of HNO3 in solution A (H=1, N=14, O=16, Na=23)

Answer 1

(HNO3) = ?
a. There are a number of indicators but I would use phenolphthalein (pH change about 8) although there are others that change at pH = 7.0
b. HNO3 + NaOH ==> NaNO3 + H2O
c1. (NaOH) = 4.00 g/dm3.
mols NaOH = 4.00/40 g/mol = 0.1 mol/dm3 = 0.1 M
c2 and c3 can't be done. You didn't give any information about the volume of HNO3 nor the volume of NaOH used.

Answer 2

Concentration of B in mol per dm3/ Molar mass= 4.00/40= 0.1
Molar mass of NaOH (23x1)+(16x1)+(1x1)= 40
Conc of solution A Ca VA/Cb Vb=na/nb
Ca? VA 24.00
Cb 0.1mol per dm3 Vb 25cm3
Cax24.00/0.1x25