Answer:
I think carbon and hydrogen
Answer;
D. carbon-12 atom
Explanation;
-One atomic mass unit is the mass that is exactly equal to one-twelfth the mass of one carbon-12 atom. Therefore, the mass of carbon-12 is 12 amu and this provides the standard that is used in measuring the atomic mass of all other elements.
-The atomic mass of carbon is 12.01 and not 12.00 in the periodic table.
-Due to the fact that there are more than one element for most naturally occurring elements, the average mass of the naturally occurring mixture of isotopes is taken while determining the atomic mass of an element.
A substance that undergoes change during a reaction, usually from coming in contact with another substance
Answer:
there are 20 oxygen atoms in 4.00 moles of Dinitrogen pentoxide
Explanation:
there are 2 atoms in an oxygen molecule , so each oxygen molecules has at least 2. Dinitrogen pentoxide is N2O5, which has 7 atoms, 2 nitrogen and 5 oxygen. 1 molecule of N2O5 has 5 oxygen atoms, so 4 of then would be 20
The molar mass of M is 0.225g/mol and the element M is Hydrogen
If a metal M combines with an oxygen element to form the oxide, 
then the chemical reaction will be expressed as:
This shows that 4 moles of an unknown element M react with the oxygen element to produce the oxide
Given the following parameters
Mass of M = 0.890 grams
Mass of = 0.956 grams
Get the molar mass of M:
Molar mass = Mass/number of moles
Molar mass = 0.890/4
Molar mass = 0.225g/mol
Hence the molar mass of M is 0.225g/mol and the element M is Hydrogen
Learn more here: brainly.com/question/6996520
