Multiple choice

Three liquids $A,B\ and\ C$ of masses $400 gm,\ 600 gm\ and\ 800 gm$ are at $30^{0}C$, $40^{0}C$ and $50^{0}C$ respectively. When $A$ and $B$ are mixed, resultant temperature is $36^{0}C$ and when $B$ and $C$ are mixed, resultant temperature is $44^{0}C$. The ratio of their specific heats are :

  1. $2:1:1$
  2. $3:2:1$
  3. $2:2:1$
  4. $1:4:9$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Heat lost = Heat gained. For A and B: 400*sA*(36-30) = 600*sB*(40-36) => 2400*sA = 2400*sB => sA = sB. For B and C: 600*sB*(44-40) = 800*sC*(50-44) => 2400*sB = 4800*sC => sB = 2*sC. Thus sA:sB:sC = 2:2:1.

AI explanation

Apply the principle of calorimetry, where mass times specific heat times temperature change is equal for both liquids during mixing. When mixing A and B, 400 * Sa * (36 - 30) = 600 * Sb * (40 - 36), which simplifies to 2400 * Sa = 2400 * Sb and shows that Sa equals Sb. When mixing B and C, 600 * Sb * (44 - 40) = 800 * Sc * (50 - 44), giving 2400 * Sb = 4800 * Sc, which means Sb equals 2 * Sc. Setting Sa = Sb = 2 * Sc, the ratio of their specific heats Sa : Sb : Sc is 2 : 2 : 1.