I’m assuming you mean barium nitrite, Ba(NO2)2.
First convert grams of Ba(NO2)2 to moles using the molar mass of Ba(NO2)2. Then use the mole ratio of 4 moles of oxygen per 1 mole of Ba(NO2)2 to convert to moles of oxygen. Then use the molar mass of oxygen to convert to grams of oxygen.
45.7 g Ba(NO2)2 • 1 mol Ba(NO2)2 / 229.35 g Ba(NO2)2 • 4 mol O / 1 mol Ba(NO2)2 • 16.0 g O / 1 mol O = 12.8 g oxygen
I’m not sure, but I think A. from an internal engine reservoir
The only reactants are Nitrogen and Oxygen and the only product is dinitrogen pentoxide. Following the law of conservation of mass, the total amount of reactants must equal the total amount of products. Thus, the total mass of dinitrogen pentoxide:
35 + 48
= 83 grams
To do this problem it is necessary to take into account that the heat given by the unknown substance is equal to the heat absorbed by the water, but considering the correct sign:

Clearing the specific heat of the unknown substance:

Answer:
Chemical change is a chemical process that occurs when a substance combines with another to create an entirely new substance, this process is also called chemical synthesis
Explanation: