experimental chemistry (chap1) -olevel pure chem

what is the SI unit for time

second (s)

SI unit for temperature

Kelvin (K)

SI unit for length

metre (m)

SI unit of mass

kilogram (kg)

SI unit for volume

cubic metre (m3)

what are some examples of insoluble gases

• hydrogen (insoluble)

• oxygen (insoluble)

• carbon dioxide (slightly soluble)

what method of collecting gases can be used for insoluble gases

water displacement

what method of collecting gases can be used for gases denser than air

downward delivery

what method of collecting gases can be used for gases less dense than air

upward delivery

what are some drying agents for drying of gases

• concentrated sulfuric acid

• quicklime (calcium oxide)

• fused calcium chloride

what gases can and cannot be dried with concentrated sulfuric acid

• not suitable for gases which react with sulfuric acid (alkaline/ basic gases)

• most gases including chlorine and hydrogen chloride

what gases can and cannot be dried with quicklime

• quicklime must be freshly heated before use

• cannot be used to dry gases that react with calcium oxide (acidic gases)

• can be used for ammonia

what gases can and cannot be dried with fused calcium chloride

• must be freshly heated before use

• cannot be used to dry gases that react with calcium chloride (eg ammonia)

• hydrogen, nitrogen, carbon dioxide (generally for neutral gases)

what are some common substances that undergo sublimation

iodine, ammonium chloride

describe the process of simple distillation of saltwater

1. the salt water is heated. boiling chips are added to ensure the liquid boils smoothly and evenly. at 100 degrees, the water boils. the vapour rises and enters the condenser.

2. the condenser provides a cool environment for the vapour to condense into liquid

3. the water vapour loses heat and cools in the condenser and condenses back to liquid water. pure water is collected in the conical flask as distiliate

what is chromatography used for

is used to separate a mixture of substances which have different solubilities in a given solvent

What are some examples of locating agents in paper chromatography

• UV lights

• ninhydrin

describe the process of fractional distillation of ethanol-water mixture

1. as the solution is heated, both ethanol and water vapour rise up the column

2. as water has a higher boiling point than ethanol, the water vapour condenses on the cool surfaces in the fractionating column and the liquid water returns to the flask

3. ethanol vapour continues to rise. it exits the column, loses heat to the cooler surface of the condenser and condenses in the condenser as a liquid and ethanol is collected first as the distilate.