Answer:
Explanation: A chemical change is a reaction in which chemical composition of the substance changes. Some bonds are broken and some new bonds are formed.
The reactants are written in terms of their chemical formula on the left hand side and the products are written in terms of their chemical formula on right hand side with a arrow in between. The chemical symbols are followed by their physical states such as (l) for liquid, (s) for solid, (g) for gas and (aq) for aqueous.
Thus the only reaction producing a gas is 
Is that a question? Doesnt seem like it
Answer:
By electroplating
Explanation:
The metal which requires to be protected from rust is connected to the anode while a lower metal in the series is connected to the cathode, the a complete circuit is made and current is passed through the circuit there by resulting to the coating of the metal at the anode.
Answer:
Uranium mines operate in many countries, but more than 85% of uranium is produced in six countries: Kazakhstan, Canada, Australia, Namibia, Niger, and Russia. Historically, conventional mines open pit or underground were the main source of uranium.
Explanation:
Hope this helps
Answer : The labs were unable to reproduce the pharmaceutical company’s data.
Explanation : Any scientific claim must have reproducible experimental data. In this case, when the pharmaceutical company has the claim of reducing the cancer growth cells by 35% then by using the same manufacturing procedure for the drug and lab should be able to get this result. But they failed to match up with the results which clearly indicates that the labs were not able to produce the same results and hence they concluded that the pharmaceutical company's claims were invalid.