Chemistry, 23.07.2019 06:20, rainbowboy9231

Agaseous compound is 78.14 percent boron and 21.86 percent hydrogen. at 27°c, 74.3 ml of the gas exerted a pressure of 1.12 atm. if the mass of the gas was 0.0934 g, what is its molecular formula?

Answers: 2

Show answers

Answers

answered: uuytay

B₂H₆

Explanation:

Given parameters:

Mass percentage of hydrogen = 21.86%

Mass percentage of boron = 78.14%

Temperature of the compound = 27°C

Pressure exerted by the gas = 1.12atm

Volume of the gas = 74.3mL = 0.0743L or 0.0743dm³

Mass of the gas = 0.0934g

Unknown:

Molecular formula of the gas = ?

We have to convert the temperature to a unit we can work with which is Kelvin:

27°C to K gives 273 + 27, which is 300K

Solution

From the mass percentages, we can derive the empirical formula of the compound.

The empirical formula is the simplest formula of a compound.

The procedure is shown below:

B H

Mass precentage 78.14 21.86

Number of moles 78.14/10.8 21.86/1

7.24 21.86

Dividing by the

smallest 7.24/7.24 21.86/7.24

1 3

The empirical formula of the compound is BH₃

To derive the molecular formula:

M.F = (E.F) x n

n is the number of repeating units of the empirical formula present in one mole.

To find the molecular formula of the gas, we use the ideal gas law to obtain the number of moles of the gas. We then proceed to find the molar mass.

ideal gas law: PV = nRT

The unknown is n, and we make it the subject of the expression:

n = $\frac{PV}{RT}$

Where P is pressure of the gas

V is the volume of the gas

R is the gas constant which is given as 0.082atmdm³mol⁻¹K⁻¹

T is the temperature

n = $\frac{1.12 x 0.0743}{0.082 x 300}$

n = 0.0034mole

From the expression:

number of moles = $\frac{mass}{molar mass}$

molar mass = $\frac{mass}{number of moles}$

molar mass = $\frac{0.0934}{0.0034}$

molar mass = 27.5g/mol of the molecular formula

From M.F = (E.F) x n we need to solve for n:

E.F is BH₃ this gives a mass of [10.8 + 3(1)] = 13.8g/mol

n = $\frac{molecular mass of the molecular formula}{molecular mass of the empirical formula}$

n = $\frac{27.5}{13.8}$ = 2

Molecular formula of the compound is then (BH₃)₂ which gives B₂H₆

answered: Guest

the answer is 1 i believe

answered: Guest

1. o2(g)as a product

Other questions on the subject: Chemistry

Chemistry, 22.06.2019 12:10, kaitlynbernatz2778

If a molecule with a molecular formula of c13h18 is treated with an excess of h2 in the presence of finally divided pt metal under conditions required for maximum hydrogenation of the molecule to give a molecule with a formula c13h24, how many rings are in the molecule?

Answers: 3

continue

Chemistry, 22.06.2019 20:30, Schoolworkspace453

Consider the following unbalanced equation for the combustion of hexane: αc6h14(g)+βo2(g)→γco2(g)+δh2o(g) part a balance the equation. give your answer as an ordered set of numbers α, β, γ, use the least possible integers for the coefficients. α α , β, γ, δ = nothing request answer part b determine how many moles of o2 are required to react completely with 5.6 moles c6h14. express your answer using two significant figures. n n = nothing mol request answer provide feedback

Answers: 2

continue

Chemistry, 22.06.2019 21:00, cody6187

Rays from the sun are not considered matter true or false

Answers: 2

continue

Chemistry, 22.06.2019 23:10, ArielA13

Amines are good nucleophiles, even though they are neutral molecules. how would the rate of an sn2 reaction between an amine and an alkyl halide be affected if the polarity of the solvent is increased? amines are good nucleophiles, even though they are neutral molecules. how would the rate of an reaction between an amine and an alkyl halide be affected if the polarity of the solvent is increased? because both reactants in the rate-limiting step are neutral, the reaction will be faster if the polarity of the solvent is increased. because both reactants in the rate-limiting step are neutral, the reaction will be slower if the polarity of the solvent is increased. because both reactants in the rate-limiting step are neutral, the reaction will occur at the same rate if the polarity of the solvent is increased. request answer

Answers: 3

continue

Do you know the correct answer?

Agaseous compound is 78.14 percent boron and 21.86 percent hydrogen. at 27°c, 74.3 ml of the gas exe...