Question

At temperature 300 K for reaction C2H4(g) + 3O2(g)→ 2CO2(g) + 2H2O(g); ΔH = −336.2 kcal. The approximate value of ΔU at 300 K for the same reaction (R = 2 cal degree− 1 mol− 1) will be-

• A. (A) −320.0 kcal
• B. (B) −335.0 kcal
• C. (C) −337.2 kcal
• D. (D) −353.0 kcal

Answer 1

Answer: (B)

(B) −335.0 kcal

Answer 2

Explanation:
f(x)=x3−3x+[a]Let [a]=t (where t will be an integer ) f(x)=x3−3x+t⇒f′(x)=3x2−3⇒f′(x)=0 has two real and distinct solution which are x=1 and x=−1so f(x)=0 will have three distinct and real solution when f(1).f(−1)<0Now,f(1)=(1)3−3(1)+t=t−2f(−1)=(−1)3−3(−1)+t=t+2From equation (ii)(t−2)(t+2)<0⇒t∈(−2,2)Now t=[a]Hence [a]∈(−2,2)⇒a∈[−1,2)