Answer:
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The main pieces of evidence that an exothermic reaction has occurred is an increase in temperature due to the release of energy, a release of energy in the form of light, or a release of gas.
Answer: The ratio of carbon dioxide molecules to oxygen molecules is 20 :31
Explanation:
Combustion is a chemical reaction in which hydrocarbons are burnt in the presence of oxygen to give carbon dioxide and water.
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.
The balanced combustion reaction is,:

Thus the ratio of carbon dioxide molecules to oxygen molecules is 20 : 31
Answer:
T₂ = 392 K
Explanation:
Given that,
Initial volume of the hot air balloon, V₁ = 55500 m³
Initial temperature, T₁ = 21°C = 294 K
Final volume, V₂ = 74000 m³
We need to find the final temperature inside the balloon. The relation between the temperature and volume is given by charles law i.e.

Where
T₂ is the final temperature
So,

So, the new temperature is 392 K.