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Charra [1.4K]
2 years ago
13

A student pours exactly 26.9 mL of HCl acid of unknown molarity into a beaker. The student then adds 2 drops of the indicator an

d titrates the acid to neutrality using 43.7 mL of 0.13 M NaOH base.
a. Write and balance the neutralization reaction of the acid and base
b. What is the molarity of the acid?
Chemistry
1 answer:
Assoli18 [71]2 years ago
6 0
a.
Acids react with bases and give salt and water and the products.

Hence, HCl reacts with NaOH and gives NaCl salt and H₂O as the products. The reaction is,
            HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)

To balance the reaction equation, both sides hould have same number of elements.

Left hand side,                                             Right hand side,
             
H atoms = 2                                               H atoms = 2
            Cl atoms = 1                                               Cl atoms = 1
            Na atoms = 1                                               Na atoms = 1 
           O atoms = 1                                                   O atoms = 1

Hence, the reaction equation is already balanced.

b. 
Molarity (M)= moles of solute (mol) / Volume of the solution (L)
 
          HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)

Molarity of NaOH = <span>0.13 M
</span>Volume of NaOH added = <span>43.7 mL
Hence, moles of NaOH added = 0.13 M x 43.7 x 10</span>⁻³ L
                                                 = 5.681 x 10⁻³ mol

Stoichiometric ratio between NaOH and HCl is 1 : 1

Hence, moles of HCl = moles of NaOH
                                    = 
5.681 x 10⁻³ mol

5.681 x 10⁻³ mol of HCl was in <span>26.9 mL.

Hence, molarity of HCl = </span>5.681 x 10⁻³ mol / 26.9 x 10⁻³ L
                                     = 0.21 M
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