Chemistry, 24.12.2019 22:31 alyssaxsanchez

1. lactic acid, which contains c, h, and o, has long been thought to be responsible for muscle soreness following strenuous exercise. when 5.000 g of lactic acid was subjected to combustion analysis, it produced 7.329 g of co 2 and 3.000 g of h 2 o.

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Answer from: Sumthin4695

The empirical formula is = CH_2O

The formula of lactic acid = $C_3H_{6}O_3$

Explanation:

Corrected from source, empirical formula and molecular formula of the lactic acid is to be determined.

Mass of water obtained = 3.000 g

Molar mass of water = 18 g/mol

Moles of H_2O = 3.000 g /18 g/mol = 0.1667 moles

2 moles of hydrogen atoms are present in 1 mole of water. So,

Moles of H = 2 x 0.1667 = 0.3333 moles

Molar mass of H atom = 1.008 g/mol

Mass of H in molecule = 0.3333 x 1.008 = 0.3359 g

Mass of carbon dioxide obtained = 7.329 g

Molar mass of carbon dioxide = 44.01 g/mol

Moles of CO_2 = 7.329 g /44.01 g/mol = 0.1665 moles

1 mole of carbon atoms are present in 1 mole of carbon dioxide. So,

Moles of C = 0.1665 moles

Molar mass of C atom = 12.0107 g/mol

Mass of C in molecule = 0.1665 x 12.0107 = 2.0001 g

Given that the Lactic acid only contains hydrogen, oxygen and carbon. So,

Mass of O in the sample = Total mass - Mass of C - Mass of H

Mass of the sample = 5.000 g

Mass of O in sample = 5.000 - 2.0001 - 0.3359 = 2.6641 g

Molar mass of O = 15.999 g/mol

Moles of O = 2.6641 / 15.999 = 0.1665 moles

Taking the simplest ratio for H, O and C as:

0.3333 : 0.1665 : 0.1665

= 2 : 1 : 1

The empirical formula is = CH_2O

Molecular formulas is the actual number of atoms of each element in the compound while empirical formulas is the simplest or reduced ratio of the elements in the compound.

Thus,

Molecular mass = n × Empirical mass

Where, n is any positive number from 1, 2, 3...

Mass from the Empirical formula = 1×12 + 2×1 + 16= 30 g/mol

Molar mass = 90.08 g/mol

So,

Molecular mass = n × Empirical mass

90.08 = n × 30

⇒ n = 3

The formula of lactic acid = $C_3H_{6}O_3$

Answer from: Quest

$\frac{239}{94}pu+\frac{1}{0}n ====> \frac{y}{z}x+\frac{134}{54}xe+3\frac{1}{0}$

the catch is that the top numbers are atomic masses the bottom numbers are the numbers of protons and electrons in an uncharged atom. they are the number of that atoms as you would find them on the periodic table. further, the numbers on the left are used to determine the missing numbers on the right

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137 subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54 subtract 54 from both sides.

40 = z

answer

$\frac{103}{40}x=\frac{103}{40}zr$

Answer from: Quest

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