Answer : The mass of oxygen formed must be 3.8 grams.
Explanation :
Law of conservation of mass : It states that mass can neither be created nor be destroyed but it can only be transformed from one form to another form.
This also means that total mass on the reactant side must be equal to the total mass on the product side.
The balanced chemical reaction will be,

According to the law of conservation of mass,
Total mass of reactant side = Total mass of product side
Total mass of
= Total mass of 
As we are given :
The mass of
= 25.3 grams
The mass of
= 23.4 grams
So,



Therefore, the mass of oxygen formed must be 3.8 grams.
Answer:
The periodic table of elements arranges all of the known chemical elements in an informative array. Elements are arranged from left to right and top to bottom in order of increasing atomic number. Order generally coincides with increasing atomic mass. The rows are called periods.
Explanation: Cause I'm smart like that!
Thermal energy is the energy of movement.
Answer:

Explanation:
= Concentration of stock solution
= Concentration of solution
= Volume of stock solution = 19 mL
= Volume of solution = 0.31 L= 310 mL
We have the relation


The concentration of the diluted solution will be 0.613 times the concentration of the stock solution.