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

Answer 1

The Correct Option is B

Explanation:
$f(x)=x^3-3x+[a]$Let $[\mathrm{a}]=\mathrm{t}\text{ (where }\mathrm{t}\text{ will be an integer })$ $f(x)=x^3-3x+t$$\Rightarrow f^{\prime }(x)=3x^2-3$$\Rightarrow f^{\prime }(x)=0$ has two real and distinct solution which are $x=1$ and $x=-1$so $f(x)=0$ will have three distinct and real solution when $f(1).f(-1)<0$Now,$f(1)=(1{)}^3-3(1)+t=t-2$$f(-1)=(-1{)}^3-3(-1)+t=t+2$From equation (ii)$(t-2)(t+2)<0$$\Rightarrow \mathrm{t}\in (-2,2)$Now $t=[a]$Hence $[\mathrm{a}]\in (-2,2)$$\Rightarrow a\in [-1,2)$