Calculate the refractive index of the substance if the speed of light in the medium is 210,000 km/s.

2.43
1.43
0.7
1.89

the second one and the forth one are in the purple because they are opinions and the rest are in the yellow

explanation:

answer: 802.3 kilo joules of energy represents 191.75 kilo calorie of energy.

explanation:

energy released during combustion of one mole methane = 802.3 kilo joules

if 1 kilo joule = 0.239006   kilo calorie

then ,802.3 kilo joule will be = 802.30.239006 kilo calorie

802.3 kilo joule = 191.75 kilo calorie

hence, the energy in kilo calorie is 191.75 kilo calorie.