Question

a solution of 500ml of 0.2m koh and 500 ml of 0.2m hcl is mixed and stirred ; the rise in temperature is t¹. the experiment is repeated using 250ml each of solution, the temperature raised is t². then what is the relationship between t¹ and t² ?​

Answer 1

Answer:

t₁ = t₂

Explanation:

The chemical equation is

KOH + HCl →KCl + H₂O

For 1st solution

Molarity of KOH = 0.2 M

i.e. in 1 L (1000 mL) no. of moles of KOH = 0.2

Therefore, in 500 mL moles of KOH = 0.1

Molarity of HCl = 0.2 M

Moles of HCl = 0.1

Heat of neutralisation Q = mcΔt

In these reactions the solutions are treated as that of pure water therefore volume of the solution in mL is equal to the weight in grams (∵ density of water = 1 gm/cc)

Total volume of the solution = 1000 ml

Therefore weight of the solution = 1000 gm

Thus,

Q = 1000cT₁

or T₁ = Q/1000c           .............. (1)

Similarly, For 2nd solution

No. of moles of KOH = 0.05

No. of moles of HCl = 0.05

SInce the moles of KOH and HCl in this solution are half to that of the 1st solution

Therefore, the heat of neutralisation will be half

Heat of neutralisation = Q/2

The mass now is 250 + 250 = 500 g

Thus

Q/2 = 500cT₂

or T₂ = Q/1000c  ...................(2)

From (1) and (2)

T₁ = T₂

Hope this answer is helpful.