Answer : The density of a sample of chlorine gas is, 12.59 g/L
Explanation :
To calculate the density of chlorine gas we are using ideal gas equation.
where,
P = pressure of chlorine gas = 4.5 atm
V = volume of chlorine gas = 12.6 L
n = number of moles of chlorine gas
w = mass of chlorine gas
R = gas constant = 0.0821 L.atm/mol.K
T = temperature of chlorine gas = 
M = molar mass of chlorine gas = 71 g/mol
Now put all the given values in the above formula, we get:
Therefore, the density of a sample of chlorine gas is, 12.59 g/L
Answer: The heat required to melt 25.0 g of ice at 
is 8350 Joules
Explanation:
Heat of Fusion tells us how much energy is needed to convert 1g of a solid to a liquid at the same temperature.
Q = Heat absorbed = ?
m = mass of ice = 25.0 g
L = Latent heat of fusion of ice = 334 J/g
Putting in the values, we get:
Thus heat required to melt 25.0 g of ice at is 8350 Joules
On temperature 25°C (298,15K) and pressure of 1 atm each gas has same amount of substance:
n(gas) = p·V ÷ R·T = 1 atm · 20L ÷ <span>0,082 L</span>·<span>atm/K</span>·<span>mol </span>· 298,15 K
n(gas) = 0,82 mol.
1) m(He) = 0,82 mol · 4 g/mol = 3,28 g.
d(He) = 10 g + 3,28 g ÷ 20 L = 0,664 g/L.
2) m(Ne) = 0,82 mol · 20,17 g/mol = 16,53 g.
d(Ne) = 26,53 g ÷ 20 L = 1,27 g/L.
3) m(CO) = 0,82 mol ·28 g/mol = 22,96 g.
d(CO) = 32,96 g ÷ 20L = 1,648 g/L.
4) m(NO) = 0,82 mol ·30 g/mol = 24,6 g.
d(NO) = 34,6 g ÷ 20 L = 1,73 g/L.
