The full question asks to decide whether the gas was a specific gas. That part is missing in your question. You need to decide whether the gas in the flask is pure helium.
To decide it you can find the molar mass of the gas in the flask, using the ideal gas equation pV = nRT, and then compare with the molar mass of the He.
From pV = nRT you can find n, after that using the mass of gass in the flask you use MM = mass/moles.
1) From pV = nRT, n = pV / RT
Data:
V = 118 ml = 0.118 liter
R = 0.082 atm*liter/mol*K
p = 768 torr * 1 atm / 760 torr = 1.0105 atm
T = 35 + 273.15 = 308.15 K
n = 1.015 atm * 0.118 liter / [ 0.082 atm*liter/K*mol * 308.15K] =0.00472 mol
mass of gas = mass of the fask with the gas - mass of the flasl evacuated = 97.171 g - 97.129 g = 0.042
=> MM = mass/n = 0.042 / 0.00472 = 8.90 g/mol
Now from a periodic table or a table you get that the molar mass of He is 4g/mol
So the numbers say that this gas is not pure helium , because its molar mass is more than double of the molar mass of helium gas.
The correct option is B.
Isotopes refers to those chemical compounds which have the same number of protons and electrons but different number of neutrons, so they end up having different mass numbers. The diagram given above is that of beryllium, which has atomic number 4 and it has 2 electrons in its outermost shell. It has four protons [same as the number of electrons] and 5 neutrons. Beryllium 10, which is its isotope has four electrons, four protons and 6 neutrons. To get the number of neutron, remove the number of electrons from the number given in the option, that is, 10 - 4 = 6.
sorry but I don't know so sorry
Answer:
Nitrogen atom is small in size than phosphorus thus the bond between its nucleus and valence electrons are stronger than phosphorus.
Hope it helps...｡◕‿◕｡
It decreases i guess. just make sure,though i'm mostly correct.
