What mass, in grams, of water would form if 4.8 grams of hydrogen reacted with 38.4 grams of oxygen?

4.8 grams of hydrogen is 2.4 moles, and 38.4 grams of oxygen is 1.2 moles. This is exactly the Stoichiometry ratio of the reaction, therefore the two will both completely react giving rise to the same total mass of water.

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.