The answer is Joule. Kilograms and Grams is a unit for weight
CH4+2O2=> 2H2O+CO2
C- 1 on both sides
H- 4 on both sides
O - 4 on both sides
When you take 7.83 g of H2, you convert to moles by dividing by the molar mass (2.02) and multiply by the number of H2s over H2Os. Then do the same for the O2. the limiting reagent in this case is the Oxygen by what I calculated.
Hope this answers your question Mariaduong159
Radiometric Dating. It's used to find the dates of ricks and other objects based on what the known decay rate of radioactive isotopes. Different forms of this method can also estimate the age of natural and man-made materials.