How is half-life period related to initial concentration for a second order reaction ?

1

(a)

t _1/2 \(\propto { a }^{ 1-n }.\) 
For n = 2, t_1/2 \(\propto a ^ {-1}\),i.e.,
t_1/2 \(\propto \) \(\frac {1}{a}\)
Thus , half-life period of a order reaction is inversely proportional to the initial concentration of the reactant.

What is the ratio of t_3/4 : t_1/2 for a first order reaction ?

1

(a)

2:1

Consider the reaction 2A + B ⟶ Products. When concentration of B alone was doubled, half life time does not change. When conc. of A alone doubled, the rate increases by two times . What are the units of K and what is the order of reaction?

1

(a)

The half life is independent of conc. of B. This means the reaction is of first order w.r.t. B and w.r.t. A also it is first order and overall order is second.

For a second order reaction 2A ⟶ Product, a plot t_1/2 vs log a (a = initial conc.), what does the intercept represent?

1

(a)

t_1/2 = 1/k .1/[Ao]
log t_1/2 = -log K – log [Ao]
Intercept = t_1/2.

What are the oxidation states of iron in Fe₃O₄?

1

(a)

\(\frac{8}{3}\) Fe₃​O₄​ is basically a mixture of Fe₂​O_3​ and FeO.

Which Substance is added to molten iron to remove sulphur impurity?

1

(a)

To satisfy low sulfur requirements for iron processed into steel, magnesium reagents in powder or granular form are used to remove sulfur via slag-liquid metal reactions done under reducing conditions, where sulfur is transferred out of the steel through the slag-metal interface, and into the slag.

During metallurgical process, in the extraction of metal, flux is added. Why?

1

(a)

Flux in the smelting process is added to, decrease the solubility of impurities, increase the fusion temperature of roasted ore and convert impurities into slag.
Flux removes the gangue to form easily fusible slag.
\(\mathrm{SiO}_{2}+\ \ \ \mathrm{FeO} \rightarrow\ \ \ \mathrm{FeSiO}_{3}\)
Acidicflux   Basicangue    Slag

Can Mg reduce Al₂O₃ and Al reduces MgO? State the conditions required for this reduction process.

1

(a)

If we look at the Ellingham diagram, it becomes evident that the plots for Al and Mg cross each other at 1350^∘C1350^∘C (1623 K). Below this temperature, Mg can reduce Al₂O₃Al₂O₃ and above this temperature, Al can reduce MgO.