Density = mass / volume
mass = density x volume
m = 0.917 x 2.5
m = 2.29 grams
Answer : The volume of gas occupy at
is, 1.25 L
Explanation :
Charles' Law : It states that volume of the gas is directly proportional to the temperature of the gas at constant pressure and number of moles.
Mathematically,

where,
are the initial volume and temperature of the gas.
are the final volume and temperature of the gas.
We are given:

Putting values in above equation, we get:

Therefore, the volume of gas occupy at
is, 1.25 L
So it contains three protons and four neutrons
Answer:
This question appears incomplete
Explanation:
This question appears incomplete because of the absence of options. However, hydrogen is placed in group 1 because it has just one electron in it's outermost shell (which happens to be the only shell it has) just like every other group 1A/group 1 element. While helium is placed in group 8A/group 18 because it has a completely filled outermost shell (which is also the only shell it has) just like every other element in group 8A/group 18.