In the reaction 2H2 + O2 --> 2H2O, how many moles of oxygen are required to fully react with 6.0 mol of hydrogen? A) 1.0 mol
B) 2.5 mol
C) 3.0 mol
D) 7.5 mol

Actually Welcome to the Concept of the Stochiometry.

Hence, here we can clearly see that, for 2 moles of Hydrogen, we need 1 mole of oxygen molecules,

so, then 6 moles of Hydrogen we need, 3 moles of Oxygen.

hence option c.) 3 mole

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.

can you attach the