Modern atomic theory is, of course, a little more involved than Dalton's theory but the essence of Dalton's theory remains valid. Today we know that atoms can be destroyed via nuclear reactions but not by chemical reactions. Also, there are different kinds of atoms (differing by their masses) within an element that are known as "isotopes", but isotopes of an element have the same chemical properties.
Many heretofore unexplained chemical phenomena were quickly explained by Dalton with his theory. Dalton's theory quickly became the theoretical foundation in chemistry.
Answer: 
Explanation:
According to ideal gas equation:

P = pressure of gas = 0.987 atm
V = Volume of gas = 12 L
n = number of moles = 0.50
R = gas constant =
T =temperature = ?


Thus the temperature of a 0.50 mol sample of a gas at 0.987 atm and a volume of 12 L is 
Answer:
One billion
Explanation:
A nanometer is a BILLIONTH of a meter which means it takes one billion to equal a meter
The number of molecules of oxygen in the cylinder is 6.02×1023 molecules
Data obtained from the question
Number of mole of oxygen = 1 mole
Number of molecule of oxygen =?
From Avogadro's hypothesis, we understood that 1 mole of any substance contains 6.02×1023 molecules. This implies that 1 mole of oxygen contains 6.02×1023 molecules.
Since the cylinder contains 1 mole of oxygen, then the number of molecules of oxygen present in the cylinder is 6.02×1023 molecules.