Chemistry, 31.07.2019 20:30 alexandra2442

A12.22 gram sample of an organic compound containing only c, h, and o is analyzed by combustion analysis and 17.91 g co2 and 7.332 g h2o are produced. in a separate experiment, the molar mass is found to be 60.05 g/mol. determine the empirical formula and the molecular formula of the organic compound.

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Answer from: rhettperkins

The empirical and molecular formula for the given organic compound is CH_2O and C_2H_4O_2 respectively.

Explanation:

The chemical equation for the combustion of hydrocarbon having carbon, hydrogen and oxygen follows:

$C_xH_yO_z+O_2\rightarrow CO_2+H_2O$

where, 'x', 'y' and 'z' are the subscripts of Carbon, hydrogen and oxygen respectively.

We are given:

Mass of CO_2=17.91g

Mass of H_2O=7.332g

We know that:

Molar mass of carbon dioxide = 44 g/mol

Molar mass of water = 18 g/mol

For calculating the mass of carbon:

In 44g of carbon dioxide, 12 g of carbon is contained.

So, in 17.91 g of carbon dioxide, $\frac{12}{44}\times 17.91=4.884g$ of carbon will be contained.

For calculating the mass of hydrogen:

In 18g of water, 2 g of hydrogen is contained.

So, in 7.332 g of water, $\frac{2}{18}\times 7.332=0.814g$ of hydrogen will be contained.

Mass of oxygen in the compound = (12.22) - (4.884 + 0.814) = 6.522 g

To formulate the empirical formula, we need to follow some steps:

Step 1: Converting the given masses into moles.

Moles of Carbon = $\frac{\text{Given mass of Carbon}}{\text{Molar mass of Carbon}}=\frac{4.884g}{12g/mole}=0.407moles$

Moles of Hydrogen = $\frac{\text{Given mass of Hydrogen}}{\text{Molar mass of Hydrogen}}=\frac{0.814g}{1g/mole}=0.814moles$

Moles of Oxygen = $\frac{\text{Given mass of oxygen}}{\text{Molar mass of oxygen}}=\frac{6.522g}{16g/mole}=0.407moles$

Step 2: Calculating the mole ratio of the given elements.

For the mole ratio, we divide each value of the moles by the smallest number of moles calculated which is 0.407 moles.

For Carbon = $\frac{0.407}{0.407}=1$

For Hydrogen = $\frac{0.814}{0.407}=2$

For Oxygen = $\frac{0.407}{0.407}=1$

Step 3: Taking the mole ratio as their subscripts.

The ratio of C : H : O = 1 : 2 : 1

Hence, the empirical formula for the given compound is $C_1H_{2}O_1=CH_2O$

For determining the molecular formula, we need to determine the valency which is multiplied by each element to get the molecular formula.

The equation used to calculate the valency is :

$n=\frac{\text{Molecular mass}}{\text{Empirical mass}}$

We are given:

Mass of molecular formula = 60.05 g/mol

Mass of empirical formula = 32 g/mol

Putting values in above equation, we get:

$n=\frac{60.05g/mol}{32g/mol}=1.87\approx 2$

Multiplying this valency by the subscript of every element of empirical formula, we get:

$C_{(1\times 2)}H_{(2\times 2)}O_{(1\times 2)}=C_2H_4O_2$

Thus, the empirical and molecular formula for the given organic compound are CH_2O and C_2H_2O_4 respectively.

Answer from: Quest

answer: the rate of diffusion increases with increase in temperature.

increase in temperature, increases the molecular/particles speed (kinetic energy. diffusion means movement of particles through the material.

generally, the heavier the particle the more it interacts with the environment and more the temperature matters. so higher temperature results in higher diffusion.

Answer from: Quest

in the given question, the partial pressure is calculated by using the ideal gas equation, that is, pv = nrt

here, p is pressure, v is volume = 25 l, n is number of moles = 0.0104 moles, r is gas constant = -0.0821 l.atm / mol.k

t is temperature = 273 k

p = nrt / v

p = (0.0104 mol × 0.0821 l.atm / mol.k × 273 k) / 25 l

= 0.0093 atm

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