B - Atomic number. Dmitri Mendeleev organised the table according to atomic weight, however this caused problems with elements such as iodine and tellurium, Iodine has a higher mass, but a lower atomic number. And to make iodine in the same group as similar elements (halogens), Mendeleev had to break his own rules and put it before tellurium in the table. Moseley fixed this problem by ordering the elements according to atomic (proton) number.
In a combustion reaction, one of the reactants is always oxygen.
Answer: The temperature of 0.6 moles of fluorine that occupy 15 L at 2,300 mmHg is 920 K
Explanation:
According to ideal gas equation:

P = pressure of gas = 2300 mm Hg = 3.02 atm (760mmHg=1atm)
V = Volume of gas = 15 L
n = number of moles = 0.6
R = gas constant =
T =temperature = ?


Thus the temperature of 0.6 moles of fluorine that occupy 15 L at 2,300 mmHg is 920 K
The pressure of the gas used in the weather balloon increases to expand the balloon.
Explanation:
- Weather balloons contain the boxes where the weather measurement instruments are present that is attached to the large balloon.
- Weather balloon uses gases like Hydrogen or Helium. When the weather balloon rises to the atmosphere, the air pressure decreases. This leads to the increase in the pressure of hydrogen or Helium gas used in the weather balloon. This expands the balloon.
- The gas particles hits the balloon container and generates the pressure. The increase of pressure thus helps the weather balloon to move in a constant speed through the atmosphere.