Organic Chemistry Flashcards
What is organic chemistry primarily concerned with?
Organic chemistry is about compounds that contain carbon.
What are hydrocarbons?
Hydrocarbons are the simplest organic compounds formed from carbon and hydrogen atoms only.
What is the general formula for alkanes?
The general formula for alkanes is CnH2n+2.
What type of bonds do alkanes have?
Alkanes have all C-C single bonds.
What are the first four alkanes?
The first four alkanes are methane, ethane, propane, and butane.
How do hydrocarbon properties change with chain length?
As the length of the carbon chain increases, hydrocarbons become less runny, less volatile, and less flammable.
What is complete combustion?
Complete combustion occurs when a hydrocarbon reacts with plenty of oxygen, producing carbon dioxide and water vapor.
What is the waste product of complete combustion?
The waste products of complete combustion are carbon dioxide and water vapor.
What is oxidation in the context of hydrocarbons?
Oxidation can be defined as the gain of oxygen.
What is a displayed formula?
A drawing showing all the atoms and bonds in a molecule is called a displayed formula.
Write the balanced equation for the complete combustion of methane (CH4).
CH4 + 2O2 → CO2 + 2H2O
What is the relationship between chain length and fuel usage?
Short chain hydrocarbons with lower boiling points are used as ‘bottled gases’ stored under pressure as liquids.
What is crude oil?
Crude oil is a fossil fuel formed from the remains of plants and animals, mainly plankton, that died millions of years ago.
How is crude oil formed?
Crude oil is formed over millions of years through high temperature and pressure acting on buried remains.
Why are fossil fuels considered non-renewable?
Fossil fuels are non-renewable because they take so long to form that they are being used up faster than they are created.
What is fractional distillation?
Fractional distillation is a process used to separate different hydrocarbons in crude oil.
What happens to crude oil during fractional distillation?
The oil is heated until most turns into gas, which enters a fractionating column.
What is a temperature gradient in a fractionating column?
In a fractionating column, the temperature is hot at the bottom and cooler at the top.
How do boiling points affect the separation of hydrocarbons?
Longer hydrocarbons with high boiling points condense and drain out early, while shorter hydrocarbons with lower boiling points drain out later.
What is the result of fractional distillation?
The crude oil mixture is separated into different fractions, each containing hydrocarbons with similar carbon atom counts.
What are hydrocarbons?
Hydrocarbons are molecules containing only hydrogen and carbon.
What is LPG?
LPG (Liquefied Petroleum Gas) contains mostly propane and butane.
Where does petrol drain in a fractionating column compared to diesel?
Petrol drains further up the fractionating column than diesel.
What is chromatography?
Chromatography is an analytical method used to separate the substances in a mixture.
What are the two phases in chromatography?
- Mobile phase - where the molecules can move (liquid or gas).
- Stationary phase - where the molecules can’t move (solid or thick liquid).
How do substances move during chromatography?
Substances constantly move between the mobile and stationary phases, forming an equilibrium.
What determines how quickly a chemical moves in chromatography?
It depends on how it’s distributed between the two phases, specifically whether it spends more time in the mobile or stationary phase.
What happens to chemicals that spend more time in the mobile phase?
They will move further up the stationary phase.
What is a chromatogram?
The result of chromatography analysis.
How is the Rf value calculated?
Rf = (distance travelled by substance) / (distance travelled by solvent).
What does a pure substance form in chromatography?
A pure substance will only ever form one spot in any solvent.
What is the stationary phase in paper chromatography?
The stationary phase is the chromatography paper (often filter paper).
What is the mobile phase in paper chromatography?
The mobile phase is the solvent (e.g., ethanol or water).
What factors affect how far a molecule travels in chromatography?
- Solubility in the solvent.
- Attraction to the paper.
What does it mean if the Rf value of a reference compound matches that of a spot in a mixture?
It is likely that the reference compound is present in the mixture.
What happens if the Rf values do not match?
The reference compound isn’t present in the mixture.
What is the significance of changing the solvent in chromatography?
The Rf value for a substance will change if you change the solvent.
What are the tests for common gases?
1) Chlorine
2) Oxygen
3) Carbon Dioxide
4) Hydrogen
How does chlorine react in a test?
Chlorine bleaches damp litmus paper, turning it white.
It may turn red for a moment first because a solution of chlorine is acidic.
What happens when a glowing splint is placed in oxygen?
The oxygen will relight the glowing splint.
How can carbon dioxide be identified?
Bubbling carbon dioxide through limewater causes the solution to turn cloudy.
What sound indicates the presence of hydrogen?
Holding a lit splint at the open end of a test tube containing hydrogen produces a ‘squeaky pop’.
The noise comes from the hydrogen burning quickly with the oxygen in the air to form water.
What is limewater used for?
Limewater is used to test for carbon dioxide.
What is a practical example of gas collection?
Hadia collects the gas given off during a reaction and bubbles it through limewater.
The limewater goes cloudy, identifying the gas produced.
Why are tests for gases considered brilliant?
They allow for nice experiments in class and include fun observations like ‘squeaky pop’.
