C-8 Chemical Analysis Flashcards
What is a pure substance
- A pure substance is a single element or compound not mixed with any other substance
What is a quality of a pure substance
- Melt and boil at specific temperatures
What can be used to determine pure substance
- Melting point
- Compare to mixtures
_ closer to boiling point the more pure
What effect do impurities have on mixtures qualities
- Effect meting and boiling point
- Low melting point and increased melting range
- Increased boiling point- increased boiling range
- What is purity in everyday language
- A pure substance is one without anything added to it
E.g Pure Milk
What is a formulation
- A formulation is a mixture that has been designed with a useful product
What are the products of formulations
Complex mixtures in which each chemical has a specific purpose
How are formulations made
- Mixing compounds carefully messed carefully to ensure properties of product-
- e.g medicine and its shell life and its curing properties
What are some example of formations
- Fuels
- Cleaning agents
- Medecine
- Paints
- Alloys
- Food
- Fertiliser
How are compounds identified
- Will have ratios or percentages of each product which gives indication
What can chromatography be used for
- Used to separate mixtures and give help identifying substances
- What does chromatography involve
- Stationary and mobile phase
What is a stationary phase
- Where molecules can’t move- solid or thick liquid
What is a mobile phase
- Where molecules can move- liquid or gas
What does separation depend on
- Distribution of substances between phases- whether it spend more tim win stationary or mobile phase
What is the calculation for the Rf value
- Distance moved by substance // Distance moved by solvent
How does chromatography work
- Constantly move between mobile and stationary phase
- Mobile phase moves through stationary phase- anything dissolved in mobile phase moves through it
- Chemicals that spend more time in mobile phase move further
- As they spend different amounts of time in mobile phase they move and end at different points
What happens to pure substances in chromatography
- Pure substances won’t separate
- What does the amount of time spent in the mobile phase depend on
- Solubility- more time in mobile phase move further-
- How attracted to paper- wills pend more time in mobile phase
How can you test for pure substances in a mixture
- Get mixture and known pure substances and run chromatography
- Compare distances of spots and if two Rf values match up- pure substance may be present
- Test in other solvent to make sure
- What is the test for chlorine
- Chlorine bleaches damp litmus paper white
- What is the test for oxygen
- Put glowing split into test tube of oxygen- if relights- oxygen is present
- What is the test for carbon dioxide
- Bubbling or shaking through calcium hydroxide- limewater- it will go cloudy
What is the test for hydrogen
- Lit splint at end of test tube- squeaky pop
