What is the molarity of the NaOH solution based on this titration? Next the stud

Question

What is the molarity of the NaOH solution based on this titration? Next the student prepares a solution of an antacid tablet (which contains solid calcium carbonate) and hydrochloric acid. They crush one tablet, add it to a beaker with^-75 mL of distilled water and add 4 drops of bromothymol blue indicator. They then add 12.1 mL of 1.00 M HCl and observe an immediate reaction. How many moles of HCl are in the 12.1 mL of 1.00 M HCl, before any reaction occurred? Write the reaction that occurs between sodium hydroxide and hydrochloric acid, as a net ionic equation.

Explanation / Answer

3.a) Molecular weight of HCl = 1+35.5 = 36.5

Now 1000 mL of 1.0 m HCl solution contains 36.5 g of HCl

Hence, 12.1 mL of 1.0 M hCl solution contains 36.5 g x 12.1 mL / 1000 mL = 0.441 g of HCl

36.5 g of HCl = 1 mole of HCl

0.441 g of HCl = 0.441/36.5 = 0.012 mole of HCl

Thus before reaction, 0.012 mole of HCl is present.

b) HCl + NaOH = NaCl + H2O

or, H+ + Cl- + Na+ + OH- = Na+ + Cl- + H2O

hence the net ionic equation is

H+ + OH- = H2O

All species are in aqueous state (aq)

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