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63 Cards in this Set

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Solvents for chromatography

Water and organic solvents (ethanol, propanol). Organic solvents are used because they dissolve substantes insoluble in water.

Precautions for using organic solvents for chromatography

Use lid to stop it from evaporating

Industrial uses of isotopes

U-235 used in nuclear power stations


Detecting level of liquid in container


Detecting leaks in underground water pipes


Controlling thickness of sheets of plastic, foil, paper, etc.

Medical uses of isotopes

Cobalt-60 used to treat internal cancer tumours.



Strontium-90 and Phosphorus-32 used to treat skin cancer tumours.



Gamma rays used to sterilize surgical equipment.



Iodine-131 used to check for dysfunctions in the thyroid gland

Alkali metals react with air to form ________ and with water to form _________.

Air=oxides


Water=hydroxides + hydrogen

Name three trends for group 1 metals

1. Reactivity increases down the group


2. Increase in density down the group


3. Decrease in melting point only (not boiling point)


Name some physical properties of alkali metals

Soft (can be cut with a knife)


Shiny when freshly cut


Low density


Low melting points


Name some chemical properties of alkali metals

React with air to form oxides


Have a valency of 1


React with water to form hydroxides and hydrogen

Reaction of Mg with steam

Mg + H²O(g) -----> MgO + H²

State the three rules for electrolysis

1. The positive ions will follow the series


2. For concentrated solutions, the halogens will be discharged first


3. For dilute solutions, and for solutions of sulfates and nitrates, the hydroxide ions will be discharged first.

Where is V2O5 (vanadium pentoxide)

In the production of sulfuric acid as a catalyst

Where is finely divided iron used?

In the Haber process, for the production of ammonia as a catalyst.

State general properties of halogens.

Reactivity decreases down the group


Gradual change in the states of matter


Colour darkens down the group


All have a valency of one


Mp and Bp increase down the group


Toxic


Poor conductors of heat


Poor conductors of electricity

Map out the limestone cycle

Bronze is made of?

Copper and tin

Brass is made of?

Copper and Zinc

Give three reasons why aluminium is used for cables

Low density (prevents sagging)


Good conductor of electricity


Resistant to corrosion

How can leakage of power from cables be prevented?

Using ceramic plates between the cable and the pylon

How is electricity conducted in metals and in ionic solutions?

Electrons carry the current in metals. Ions carry the charge in solutions.

Where does oxidation and reduction occur in electrolysis?

Reduction at cathode where metal is formed as ions gain electrons. Oxidation at anode where non metals are formed as ions lose electrons.

Why do we electroplate?

For attractive appearances


For protective coating (eg to prevent rusting)

Three precautions for electroplating.

-object must be clean and free of grease otherwise impurities will interfere with the coating giving a rough texture that will flake off



-object must be rotated to get the coating evenly on all sides



-must be carried out in careful control: temperature, current and the concentration of the electrolyte must be precise otherwise the layer will form too fast and flake off.

What is the catalyst used for the decomposition of hydrogen peroxide? Write an equation for the reaction.

Manganese (IV) oxide.


2H2O2(l) ----> 2H2O(l) + O2(g)

Name the catalyst for the following industrial processes:


1. Manufacture of nitric acid (oxidation of ammonia)


2. Methanol to hydrocarbon conversion

1. Platinum-rhodium


2. Zeolite

How do catalysts work?

A catalyst increases the rate of reaction by reducing the amount of energy needed for the bonds to break. This reduces the activation energy of the reaction and makes sure there are more frequent collisions.

Give three equations for photography from silver bromide and provide an explanation for each.

2AgBr ----> 2Ag + Br2


Silver bromide crystals decompose in the presence of sunlight. The precipitates (AgBr) darken in the presence of sunlight. This is a redox reaction:



- bromide ions lose electrons (they are oxidized) 2Br- -2e ----> Br2



-silver ions gain electrons (they are reduced) Ag+ +e -----> Ag



So, in photography, silver ions are converted into silver atoms. This is the basis of photography.





2Ag

FLAME TESTS FOR:


• Li


• Na


• K

Lithium is red.


Sodium is yellow.


Potassium is lilac.

Colour of transition metals in solution:


• Copper


• Chromium


• Cobalt


• Chromate


• Dichromate


• Managanate

Cooper is blue.


Chromium is green.


Cobalt is pink.


Chromate is yellow and dichromate is orange.


Managanate is purple.

Five uses of limestone.

1. Used with sand and NaCO3 to make glass.


2. Used to make cement.


3. Used for neutralization of acidified lakes and soils.


4. Used to make concrete.


5. Used to remove impurities in the production of steel.

What type of reaction forms the basis of electrolysis and what type forms the basis of cells? Explain why.

Electrolysis is endothermic: energy is being supplied. The energy is converted from electrical to chemical.



Simple cells involve exothermic relations: energy is being produced. We use chemical energy to produce electricity.

Explain the principle of simple cells.

Zn loses electrons (oxidation) to form ions therefore becoming the negative electrode.


Zn - 2e ----> Zn+²



Cu ions gain electrons (reduction) to become copper atoms.


Cu²+(aq) + 2e ----> Cu(s)



Overall reaction:


Zn(s) + Cu²+ (aq) ----> Zn²+(aq) + Cu(s)

How does a fuel cell work?

Forms the basis of an electrochemical cell. It consists of an oxidant which reacts with a fuel in a redox reaction to release energy.

Explain the functioning of a fuel cell using hydrogen as fuel.

When oxidized, hydrogen forms water. The fuel cell consists of two electrodes sandwiched around an electrolyte. Hydrogen is fed to the anode and Oxygen is fed to the cathode. A catalyst activates the hydrogen atoms to separate into protons (H+) and electrons. The electrons flow through the external circuit, creating a current while the protons travel through the electrolyte, to the cathode, where they unite with oxygen and the electrons to produce water.



A: 2H2 + 4e ----> 4H+


C: O2 + 4H+ +4e ----> 2H2O


OVERALL:


2H2 + O2 -----> 2H2O

What are the products of complete combustion of hydrocarbons?

Carbon dioxide and water. It is al also an exothermic reaction.

Pros and cons of fuel cells with hydrogen as a fuel.

PROS:



- Very clean production of energy.


- Less opportunity of losing potentially useful energy as there are few staged of energy production.


- No carbon dioxide emissions


- Nontoxic



CONS:


- Large fuel tank required


- Currently expensive


- Difficult to store in one place

Rules for assigning oxidation numbers.

1. Ox no for any uncombined element is 0. (Eg O2, Xe, C)


2. Ox no of a monoatomic ion equals to it's charge.


3. Ox no of fluorine in a compound is always -1.


4. Oxygen has ox no of -2 unless combined with F when it is +2 or when in peroxide when it is -1.


5. Ox no of hydrogen in most compounds is +1 (HCl) unless combined with metal where it is -1 (NaH)


6. In compounds, group 1, 2 and Aluminium elements have ox nos 1, 2 and 3 respectively.


7. Sum of ox nos in a neutral compound is 0.


8. Sum of ox nos in polyatomic ions is equal to it's charge.

Define oxidation, and reduction

Oxidation is loss of electrons. Reduction is gain.



Oxidation is gain of oxygen, reduction is loss.



Oxidation is increase in oxidation number, reduction is decrease.



Oxidation is loss of hydrogen, reduction is gain.

Define oxidising agents. Give examples.

Cause oxidation reactions to take place. Gain electrons from other atoms or ions and are therefore themselves reduced. Eg: potassium manganate, potassium dichromate, hydrogen peroxide and oxygen.

Define reducing agents. Give examples.

Cause reduction reactions to take place. Lose/donate electrons to other substances and are thus oxidized themselves. Eg: Carbon, hydrogen, carbon monoxide.

Test for oxidizing agents.

Addition of KI (Potassium Iodide)


Colourless to yellow brown.


2I- -2e ----> I2

Test for reducing agents.

Addition of acidified potassium manganate: purple to colourless.



Addition of acidified potassium dichromate: orange to green.

Chemical test for water

CuSO4.5H2O <-----> CuSO4 + 5H2O


(Blue is hydrated) to (white is anhydrous)

Define reversible reactions.

Reactions in which products can be converted back into their original state as a reactant.

Define Le Chatelier's Principle.

When a system in dynamic equilibrium is stressed, the system moves so as to oppose gbr change in order to restore the equilibrium.

Factors affecting equilibrium positions.

Concentration.


Pressure (only for systems in gaseous states): increasing the pressure shifts the equilibrium to the side with fewer moles.


Temperature: increase in temperature causes the system to favor an endothermic reaction. Decrease in temperature favours an exothermic reaction.

State the conditions for the Haber process. Write the equation.

450°C temperature.


200 atm.


Catalyst of finely divided iron.



2N + 3H2 ----> 2NH3


(Forward reaction is exothermic, so a lower temperature is preferred with increased pressure).

State the equation for the Contact process. Write the conditions.

450°C temperature


1 atm


Vanadium pentoxide as catalyst.



Exothermic reaction is the forward reaction so a lower temperature is preferred.



2SO2 + O2 ----> 2SO3

Three uses of sulfur.

• To vulcanize rubber (in order to make it harder and more elastic)


• As a sterilizing agent


• To manufacture matches, fireworks.

Three uses of sulfur dioxide.

• Used in the Contact process for the production of sulfuric acid.


• Used as a bleach in making paper from wood pulp.


• Used as a food preservative by killing bacteria.

Three uses of sulfuric acid.

Used in the manufacture of paint and dyes.


• Used in producing soaps and detergents.


• Used in dyes, fabrics and polymers.

Explain the manufacture of H2SO4.

- sulfur burnt in air to produce sulfur dioxide. S + O2 ---> SO2


- sulfur further oxidized to sulfur trioxide in contact process.


- SO3 is dissolved in conc H2SO4. The solution formed means the acid can be transported in concentrated form and diluted on site. SO3 + H2SO4 ----> H2S2O7 (oleum)


- oleum is then diluted to make sulfuric acid. H2S2O7 + H2O ----> 2H2SO4


Why isn't sulfur trioxide directly dissolved in water to produce sulfuric acid?

The reaction is extremely exothermic and so very violent producing an acid mist which is detrimental to the environment.

Uses of chlorine.

• to kill bacteria in water


• in making bleach


• to make plastic PVC

Uses of fluorine

• in toothpaste


• in non stick coating for pans

Uses of bromine

• in pesticides


• in photography from it's salts


• flame retardants


• petrol additives

Uses of iodine

• photography paper and film


• as an antiseptic

How is cement made? Also concrete? Mortar?

Powdered limestone is mixed with clay in a rotary kiln to make cement. Cement is mixed with aggregate to make concrete. Ca(OH)2 is mixed with sand to make mortar.

Explain the manufacturing of hydrogen through methane and water.

1. DESULPHERIZATION: methane is purified to remove sulfurous impurities that could poison the catalyst.


2. STEAM REFORMER: methane reacts with steam to form CO and H2 in 700°C, 30 atm and nickel catalyst.


3. SHIFT REACTOR: CO reacts with steam to form CO2 and H2.


4. ABSORBER: mixture of CO2 and H2 passes through a basic solution which removes CO2.


5. HYDROGEN IS SERVED.

What do displacement reactions for ammonia produce?

When ammonia salts displace by more reactive bases, they produce ammonia and water.

Uses of ammonia.

• used to manufacture fertilizers


• used as a household cleansing agent


• used to produce nitric acid

What type of reaction is breaking and forming bonds?

Breaking binds takes in energy and so is endothermic. Forming binds gives out energy and is exothermic.

How is lime produced?

By the decomposition of calcium carbonate in a lime kiln. An open system where equilibrium is not possible as the carbon dioxide gas escapes. Carrying the reaction out in a closed container would make it reversible and not that much of limestone will be decomposed.

Uses of aluminium

In cables.


In aluminium foil


In buildings and windows