substance δh°f (kj/mol)
so2 (g) −297
answer : the mass of the helium in the blimp is, 1.1216 kg
solution : given,
volume of helium in the blimp =
density of helium in the blimp =
formula used :
now put all the given values in this formula, we get the mass of helium in the blimp.
therefore, the mass of the helium in the blimp is, 1.1216 kg
the answer is cohesive
assume that you have 100 g of the compound.
then you have 85.71 g of c and 14.29 g of h.
1. calculate the moles of each element.
moles of c = 85.71 × 1/12.01 = 7.130 mol c
moles of h = 14.29 × 1/1.008 = 14.18 mol h
2. calculate the molar ratios.
divide all values by the smallest number.
c: 7.130/7.130 = 1
h: 14.18/7.130 = 1.986
3. determine the empirical formula
round off all numbers to the closest integer.
the empirical formula (ef) is ch₂.
4. calculate the ef mass
ef mass = (12.01 + 2.016) u
ef mass = 14.03 u
5. calculate the moles of compound
stp is 0 °c and 1 bar.
1 mol of a gas occupies 22.71 dm³ at stp.
56 cm³ = 0.056 dm³ convert to moles
= 0.056 × 1/22.71
= 2.47 × 10⁻³ mol
6. calculate the molar mass
mm = mass/moles
= 0.070 g/2.47 × 10⁻³ mol
= 28.39 g/mol
7. calculate the molecular formula (mf)
the molecular formula is an integral multiple of the empirical formula.
mf = (ef)ₙ
n = mf mass/ef mass
= 28.39 u/14.03 u
mf = (ch₂)₂
the molecular formula is c₂h₄.
a. atoms gain, lose, or share electrons to achieve a full valence shell.