Consider the following intermediate chemical equations.

what is the enthalpy of the overall chemical reaction?
-999 kj
-250. kj
250. kj
999 kj

999 kJ

Explanation:

Given are two reactions with enthalpies Δ and Δ

We know enthalpy is an additive property.

Thus the overall chemical equation can be obtained from adding both the two elementary equations.

Therefore the overall enthalpy is the summation of enthalphy change in each equation.

ΔΔΔ

Δ

Therefore the overall enthalpy is 999 kJ.

the answer is a. co2, this would be colder than the : )

explanation:

in scientific notation, the value of the  speed of light in a vacuum

  will be written as 2.995 * 10^8. when this value is represented in the form of

  a * 10^b, then, a = 2.995 and b = 8.

the value of the speed of light in a vacuum given above can also be rounded up to approximately 300000000. in this case, the scientific notation will be written as 3 *10^8.