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Balancing chemical equationsChemistryHigh schoolabout 1:15

Balance the chemical equation C8H18 + O2 → CO2 + H2O: animated lesson

A narrated, step-by-step balancing chemical equations video lesson with captions. Final answer: 2C8H18 + 25O2 → 16CO2 + 18H2O.

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Video with a synthetic English voice and captions. Pick another language for subtitles in that language, or open the interactive version.

Video narrated by a synthetic voice (Piper TTS, en_US-ljspeech-high voice (LJ Speech dataset, public domain)); the steps come from our maths engine and the answer was checked independently. Download MP4 (0.5 MB) · Captions (WebVTT)

Steps on screen

1. The problem
Worked example
Balance the chemical equation C8H18 + O2 → CO2 + H2O.
2. Step by step
1. $\text{C}: 8c_{1} = 1c_{3} \\ \text{H}: 18c_{1} = 2c_{4} \\ \text{O}: 2c_{2} = 2c_{3} + 1c_{4}$
  Write an atom balance for each element
2. $c_{1} = 2,\ c_{2} = 25,\ c_{3} = 16,\ c_{4} = 18$
  Solve the linear system with the smallest whole numbers
3. $2\mathrm{C_{8}H_{18}} + 25\mathrm{O_{2}} \rightarrow 16\mathrm{CO_{2}} + 18\mathrm{H_{2}O}$
  Balanced equation
3. The answer
$2\mathrm{C_{8}H_{18}} + 25\mathrm{O_{2}} \rightarrow 16\mathrm{CO_{2}} + 18\mathrm{H_{2}O}$
2C8H18 + 25O2 → 16CO2 + 18H2O
4. Check
- C: 16 = 16, H: 36 = 36, O: 50 = 50 ✓

Transcript

The problem. Here is the problem: Balance the chemical equation C8H18 plus O2 → CO2 plus H2O. Balance atoms of every element, then use the coefficients as mole ratios.

Step by step. Write an atom balance for each element. Give each species an unknown coefficient; atoms of every element must be equal on both sides. Solve the linear system with the smallest whole numbers. Exact elimination leaves one free coefficient; scaling by the least common denominator gives integers. Balanced equation.

The answer. So the answer is 2C8H18 plus 25O2 → 16CO2 plus 18H2O. Coefficients in a balanced equation count particles (moles), not grams. Convert grams to moles, apply the mole ratio, then convert back to grams with the other species prime molar mass. Assumes the reaction goes to completion with the known species fully consumed (or formed).

Check. C: 16 equals 16, H: 36 equals 36, O: 50 equals 50, which checks out.

About balancing chemical equations

Balance chemical equations so every element has the same number of atoms on both sides.

Balance the chemical equation C8H18 + O2 → CO2 + H2O