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:
Correct answer is A.
Explanation:
Frequency is the number of oscillations that a wave have per unit time. Since time is measured in seconds, the wave with the highest frequency must register the highest number of oscillation per second. Hence, correct answer is A.
Answer:
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Answer:
Knowing that boron has an atomic mass of 10,811 means that all boron isotopes on average weigh 10,811 u.
Explanation:
The atomic mass of an atom is the mass of the atom measured in u (unified atomic mass unit), although we can also express it as Da (Dalton's unit)
Atomic mass refers to the average mass that all isotopes of that element have.
When we speak of isotopes we are referring to the element itself but with a different number of neutrons, which makes it modify its mass number.