MCQ
Which of the following may be colourless
- A$C{r^{ + 3}}$
- ✓$C{u^ + }$
- C$F{e^{ + 3}}$
- D$C{u^{2 + }}$

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$CO + \frac{1}{2}{O_2} \to C{O_2};\,\Delta H = - 24\,kJ$ The heat of formation of $C{O_2}$ is .....$kJ$
