Which of the following solutions will have pH close to 1.0 ?

100 ml of 0.1 M HCl + 100 ml of 0.1 M NaOH
55 ml of 0.1 M HCl + 45 ml of 0.1 M NaOH
75 ml of 0.2 M HCl + 25 ml of 0.2 M NaOH
10 ml of 0.1 M HCl + 90 ml of 0.1 M NaOH

Solution

Milli moles of HCl = 75 × 0.2 = 15;
Milli moles of NaOH = 25 ×0.2 =5
Milli moles of HCl left un-neutralized = 15 – 5 = 10 ;

[H₃O⁺] = \(\frac{10}{75+25}\) = 0.1M; pH = 1

For a certain reaction, rate = k × [H+]n. If pH of reaction changes from two to one, the rate becomes 100 times of its value at pH = 2, the order of reaction is –

1
2
zero
3

Solution

Solution

At 25ºC the pH of 0.01 M KOH is 12. If the temperature of this solution is raised to 50ºC without changing the volume,which of the following is correct ?

Both pH and pOH will remain constant
pH will decrease while pOH will remain constant
pH will increase whilepOH will remain constant
pH will increase while pOH will decrease

Solution

KOH, being strong electrolyte, ionizes completely.Hence [OH–] = 0.01 M which remains constant, even at 50ºC (volume of solution is supposed to be constant). Hence,pOH(= –log 0.01 =2) remains constant. At 50ºC pK_w< 14. Hence pH at 50ºC = (pK_w– 2) < 12

Solution

Two samples of CH₃COOH each of 10gm were taken separately in two vessels containing water of 6 litre and 12 litre respectively at 27°C. The degree of dissociation of CH₃COOH will be –

More in 12 litre vessel
More in 6 litre vessel
Equal in both vessels
Half in 6 litre vessel than in 12 litre vessel

Solution

The pH of a solution containing equimolar amounts of CH₃COOH (pK_a= 4.74 at 25ºC) and sodium acetate at 50ºC is :

4.74
< 4.74
> 4.74
none of these

Solution

Solution

A solution of NH₄Cl and NH₃ has pH = 8.0. Which of the following hydroxides may be precipitated when this solution is mixed with equal volume of 0.2 M of metal ion.

Ba(OH)₂(K_sp = 1.1 × 10^-4)
Mg(OH)₂(K_sp = 3.5 × 10^-4)
Fe(OH)₂(K_sp = 8.1 × 10^-16)
Ca(OH)₂(K_sp = 2.1 × 10^-5)

Solution

What is the correct relationship between the pHs of isomolar solutions of sodium oxide (pH₁), sodium sulphide (pH₂), sodium selenide (pH₃) and sodium telluride (pH₄)?

pH₁ > pH₂ > pH₃ > pH₄
pH₁ > pH₂ \(\equiv\) pH₃ > pH₄
pH₁ < pH₂ < pH₃ < pH₄
pH₁ < pH₂ < pH₃ \(\equiv\) pH₄

Solution

The solution formed from isomolar solutions of sodium oxide,sodium sulphide, sodium selenide are H₂O, H₂S,H₂Se& H₂Te respectively.As the acidic strength increases from H₂O to H₂Te thus pH decreases and hence the correct order of pH_s is pH₁ > pH₂ > pH₃ > pH₄.

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