Choose the correct statements about the Ellingham diagram for oxides (standard Gibbs energy per mole of $O X_{2}$ against temperature).

ALines for most metal oxide formations slope upward because gaseous $O X_{2}$ is consumed.
BThe line for $2 CO + O X_{2} 2 CO X_{2}$ has a positive slope.
CBelow about 983 K, carbon is thermodynamically a better reducing agent than $CO$ .
DThe line for $2 C + O X_{2} 2 CO$ has a negative slope.

Answer: A, B, D

The

2 C + O X_{2} 2 CO

line falls because gas moles increase, and the

2 CO + O X_{2} 2 CO X_{2}

line rises because gas moles decrease. Metal oxide formation consumes

O X_{2}

, so

Δ S^{\circ} < 0

and the line rises. Below about 983 K the

CO

line is lower than the carbon-to-

CO

line, so

CO

is the better reductant there and the fourth statement is false.