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1) 0.90 g of hydrogen chloride ( H C l ) is dissolved in water to make 2.5 L of

ID: 795011 • Letter: 1

Question

                    1)
                    0.90g of hydrogen chloride (HCl) is dissolved in water to make                     2.5L of solution. What is the pH of the resulting hydrochloric acid solution?
                    Kw=[H=][OH-]=1.00*10^-14
                

                    
                    
                

                    2)
                    0.40g of sodium hydroxide (NaOH) pellets are dissolved in water to make 5.0L of solution. What is the                     pH of this                     solution?
                    Kw=[H=][OH-]=1.00*10^-14                 

Explanation / Answer

no. of moles of HCl= 0.9/36.5 = 0.025 moles

molarity of the solution= .025/2.5 = 0.01M

molarity of hydronium ion= 0.01M

pH of the solution= -log(0.01) = 2 (answer)


no. of moles of NaOH= 0.4/40 = 0.01 moles

molarity of the solution= .01/5 = 0.002M

molarity of hydroxyl ion= 0.002M

pOH of the solution= -log(0.002) = 2.7

i.e., pH of the solution= 14-2.7 = 11.3 (answer)