TOPIC 3 - Quantative Chemistry

Why is aluminium more expensive than carbon?:

more energy is needed to obtain it; because electrolysis is used

Indicators?:

phenolphthalein - pink to colourless (alkali - acid/ neutral); litmus - blue to red (alkali - not)

Explain why the pH of an acid depends on the strength and conc of it?: 

• Generally, pH depends on the H+ ion conc

• the higher the conc of H+ ions, the lower the pH

• Strength: the stronger the acid, the greater the ionisation

• so the stronger the acid, the lower the pH

• Conc: the higher the con of an acid in the same volume of solution, the higher the conc of H+ ions so lower pH

why did the electrical conductivity of the neutralised solution become 0?:

the product was an insoluble solid; so no ions are free to move; H+ reacted with OH- ions to produce water

Why can the gas collected be less than the gas produced?:

some gas can escape the flask before the stopper is put in

How does increasing the temperature affect the rate of reaction?:

increasing the temperature, increases the rate of reaction; because the particles have more kinetic energy; so there are more frequent successful collisions

How to calculate the uncertainty of a result?:

work out the range; divide it by 2 (add to on to the mean)

Instead of "a spatula of powder", what would be better to say?:

use the same mass of powder

Test for double C-C bond?:

add bromine water; changes from brown-orange to colourless

Why are high atom economy reactions used in business?:

for sustainable development; for economic reasons; to produce a higher percentage of useful product

What can react with limestone to cause erosion?:

acid rain

What do particles of soot in the air cause?:

global dimming

Why is carbon reduction not used to extract aluminium?:

Aluminium is more reactive than carbon; so carbon can't displace aluminium

How can an investigation be improved to ensure the reaction is complete?:

reheat; and reweigh until the mass is constant

Why is copper used in the manufacture of computers?:

it is a good conductor of electricity

What are the reasons why iron from the blast furnace is converted into steel?:

to make alloys for specific uses; iron is brittle but steel is strong/ flexible

Apart from cost, give three different reasons why steel should be recycled: 

• to conserve resources of iron/ iron ore

• to avoid the need for quarrying/ mining 

• to conserve energy resources or fossil fuels

• to limit CO2 produces; reduced global warming

• to reduce to amount of landfill

Name the type of reaction that happens when a metal carbonate is heated:

thermal decomposition
(forms copper oxide)

Iron ores must contain enough iron to ___?:

make it economical to extract the iron