The mass defect in a particular reaction is $$0.4$$ g. The amount of energy liberated is $$n \times 10^7$$ kW h, where $$n$$ = _____. (speed of light $$= 3 \times 10^8 \text{ m s}^{-1}$$)

$$E = \Delta m \cdot c^2 = 0.4 \times 10^{-3} \times (3 \times 10^8)^2 = 0.4 \times 10^{-3} \times 9 \times 10^{16} = 3.6 \times 10^{13}$$ J.

Converting to kWh: $$\frac{3.6 \times 10^{13}}{3.6 \times 10^6} = 10^7$$ kWh = $$1 \times 10^7$$ kWh.

So $$n = 1$$.

The answer is $$\boxed{1}$$.