Ammonia (nh3) burns in air to form nitrogen dioxide and water. calculate grams of nitrogen dioxide produced if 4.0 grams of ammonia are consumed

The balanced equation for the above reaction is;
4NH₃ + 7O₂  --> 4NO₂  + 6H₂O
stoichiometry of NH₃ to NO₂ is 4:4
the number of NH₃ moles consumed are - 4.0 g / 17 g/mol = 0.24 mol
number of NH₃ moles reacted are equivalent to number of NO₂ moles formed 
therefore number of NO₂ moles formed - 0.24 mol x 46 g/mol = 11.04 g
mass of NO₂ formed is 11.04 g

Law of conservation of mass

Ernest Rutherford

Explanation:

The basic law of behavior of matter that states that "mass is neither created nor destroyed in a chemical reaction or physical change".

This is the law of conservation of mass. It is very essential in understanding most chemical reaction. Also, in quantitative analysis, this law is pivotal.

Ernest Rutherford was the scientist that stated that the nucleus is made up of positive charge. It was not until James Chadwick in 1932 discovered the neutron that we had an understanding of this nuclear component.

Rutherford surmised from his experiment that because most the alpha particles passed through the thin Gold foil and just a tiny fraction was deflected back, the atom is made is made up of small nucleus that is positively charged.