Question

CH 112 Date Section Instructor Name Team Pre-Lab Questions 1. What is the difference between an Arrhenius base and a Brønsted-Lowry base? 2. Why are acid-base reactions called neutralization reactions? 3. What does the pH of a solution tell you? : Properties of Acids and Bases Acid Base Neutral af with Unknown

Answer 1

Answer:-

(1)-

According to the "Arrhenius concept of acid and base" , an acid is that substance which gives H⁺ or H₃O⁺ ions in its aqueous solution whereas a base is that substance which gives OH^- ions in its aqueous solution. Therefore Arrhenius acids are as follows:-

(i) HCl + H₂O   $\rightarrow$ H₃O⁺_(aq)    + Cl^-_(aq)  

acid

(ii) H₂SO₄ + 2H₂O   $\rightarrow$ 2H₃O⁺_(aq)    + SO₄^--_(aq)  

acid

(i) HNO₃ + H₂O   $\rightarrow$ H₃O⁺_(aq)    + NO₃^-_(aq)  

acid

So Arrhenius bases are as follows:-

(i) NaOH + H₂O   $\rightarrow$ Na⁺_(aq)    + OH^-_(aq)  

base

(ii) Ca(OH)₂ + 2H₂O   $\rightarrow$ Ca⁺⁺_(aq)    + 2OH^-_(aq)  

base

(i) KOH + H₂O   $\rightarrow$ K⁺_(aq)    + OH^-_(aq)  

base

Also we know that according to the "Bronsted -Lowry concept of acid and base" an acid is that substance which has tendency to donate a proton (H⁺ ) to any substance whereas a base is that substance which has tendency to accept a proton (H⁺ ) from any substance. Therefore Bronsted -Lowry acids are as follows:-

(i) H₃O⁺_(aq)      $\rightarrow$ H⁺_(aq)    + H₂O_(l)

acid

(ii) H₂SO₄    $\rightarrow$ 2H⁺ + SO₄^--

acid

(i) HNO₃      $\rightarrow$ H⁺ + NO₃^-  

acid

So  Bronsted -Lowry bases are as follows:-

(i) H₂O_(l) +    H⁺    $\rightarrow$    H₃O⁺_(aq)  

base

(ii)   NH_3(l) +    H⁺   $\rightarrow$ NH₄⁺  

base

(i)    Cl^- + H⁺   $\rightarrow$ HCl

  base

Therefore we can say that there is major difference between Arrhenius bases and Bronsted -Lowry bases because Arrhenius bases are those substance which produced OH^- ions on their aqueous solution which shows that substance must have OH moiety in their chemical formula and this concept of base is only applicable to aqueous solution of bases whereas Bronsted -Lowry bases are those substance which have tendency to accept proton (H⁺) which shows that it is not limited to aqueous solution of base which must have OH moiety in their chemical formula. According to this concept water (H₂O) , ammonia (NH₃) and negative ions (Cl^-) are bases which don't have OH moiety in their chemical formula.

(2)-

As we know that neutralization reaction is that reaction in which an acid reacts with a base to form salt and water. Generally in neutralization reaction , there is reaction between H⁺ ion of an acid and OH^- ion of the base to form neutral water (H₂O). therefore acid base reactions are called as neutralization reaction because there is formation of  neutral water (H₂O) molecule when reaction between H⁺ ion of an acid and OH^- ion of the base occurs. e.g.

HCl + NaOH   $\rightarrow$ NaCl + H₂O

acid base salt water

above reaction can be written as follows:-

H⁺ +  Cl^- + Na⁺ + OH^-   $\rightarrow$   Na⁺ + Cl^-      + H₂O_(l)

Total ionic reaction of neutralization reaction

So net ionic equation can be written by ignoring spectator ions (Na⁺ and Cl^- ) in the equation.

H⁺ + OH^-   $\rightarrow$     H₂O_(l)

Net ionic reaction of neutralization reaction

(3)-

As we know that pH stands for potential of Hydrogen. pH of any solution tells us the nature of solution which means that the solution is acidic , basic or neutral in nature. pH of any solution determine the concentration of H⁺ or H₃O⁺ ions in the solution . pH of the solution is defined as the negative logarithm of its H⁺ or H₃O⁺ ion concentration.

therefore

pH = - log[H⁺]

or

pH = - log[H₃O⁺]

Also we know that The nature of an aqueous solution (acidic , basic or neutral) depends upon the concentration of H⁺ ions or OH^- ions present in the solution. Pure water has equal concentration of H⁺ ions and OH^- ions. If the concentration of H⁺ ions is greater than that of OH^- ions , the solution is acidic . If the concentration of OH^- ions is greater than that of H⁺ ions , the solution is basic.

So

pH = 7 (solution is neutral)

pH < 7 (solution is acidic )

pH > 7 (solution is basic ).