Unit 3 - Elements of Change- Combustion, Carbon, and Climate

Combustion reaction: occurs when fuel burns in oxygen

Incomplete combustion: when there’s not enough access to oxygen, leaving carbon monoxide carbon and water

Complete combustion: Creates carbon dioxide and water

What are fuels usually made of? hydrogen, carbon and sometimes sulfur

How much CO2 will be produced if 50 kg of C3H8 burns completely in oxygen?

C3H8+ (5)O2 → (4)H2O + (3)CO2

1. Calculate the moles of C3H8:

   • The molar mass of C3H8 (propane) is approximately 44.1 g/mol (just add up the atomic masses)

   • Convert 50 kg to grams: 50 kg = 50,000 g.

   • Moles of C3H8 = mass (g) / molar mass (g/mol) = 50,000 g / 44.1 g/mol ≈ 1131.3 moles.

2. Use the balanced equation:

   • The equation C3H8 + (5) O2 → (4) H2O + (3) CO2 indicates that 1 mole of C3H8 produces 3 moles of CO2.

   • Therefore, moles of CO2 produced = moles of C3H8 × 3 = 1131.3 moles × 3 ≈ 3393.9 moles.

3. Calculate the mass of CO2 produced:

   • The molar mass of CO2 is approximately 44.01 g/mol.

   • Mass of CO2 = moles × molar mass = 3393.9 moles × 44.01 g/mol ≈ 149,971 g or approximately 149.97 kg.

Empirical formula: shows the simplest ratio of atoms present for example C2H6 would be CH3

Condensed formula: written according to the structure of the compound, for example, ethene (C2H4) would be H2C=CH2

A hydrocarbon with 1 carbon: Meth-

A hydrocarbon with 2 carbons: Eth-

A hydrocarbon with 3 carbons: Prop-

A hydrocarbon with 4 carbons: But-

A hydrocarbon with 5 carbons: Pent-

A hydrocarbon with 6 carbons: Hept-

A hydrocarbon with 7 carbons: Sept-

A hydrocarbon with 8 carbons: Oct-

A hydrocarbon with 9 carbons: Non-

A hydrocarbon with 10 carbons: Dec-

Isomers: Same chemical formula but different structures

_ Methyl: a branch, putting a number before with commas to show where the branch is located

Alkenes: End in -ene and have 1 or more double carbon bond

How do we show a double bond in an alkenes?

You show by writing the number in which the double bond is in between ( for example but-1-ene, or but-2-ene)

_,_ Dimethyl: 2 branches putting 2 numbers before with commas to show where the branch is located

_,_,_ trimethyl: 3 branches putting 3 numbers before with commas to show where the branch is located

Alkynes: when there is a triple bond between two carbons

Halgenoalkanes: when they got extras, for example, chlorine, adding chloro- to the top. You also add a number at the start showing which carbon they are bonded to.

Alcohols: when they contain OH on one of the branches instead of just hydrogen

Exothermic: releases thermal energy, creating a product with less energy than the reactants

Endothermic: Absorbs thermal energy, creating a product with more energy than the reactants

Breaking bonds absorb energy, making a positive energy

Creating bonds creates energy, making a negative energy

When delta H is positive the reaction is endothermic

When delta H is negative the reaction is exothermic