Metals and apparatus Flashcards
Criterion B: 6 questions.
Research questions, hypothesis(with scientific reason), Variables, safety measures (and hazards), materials, procedures.
Weighing machine
Measure the mass of any object, apparatus or chemical in the laboratory.
Stirrer
Magnetic, motor, glass rod, used to mix or to reduce adhesion between sides of the glassware and the contents within.
Electrode
An electric conductor which passes electricity to a non-metallic substance.
Electrochemical cell electrodes
Cathode (entering of electrical charge), Anode (leaving of electrical charge)
Spirit lamp/ Alcohol burner
Used to produce an open flame, made of metals.
Battery
A device consisting of one or more electrochemical cells. Used for powering electrical devices.
When connected to an electric load, a redox reaction converts high energy reactants to low energy products while the energy produced is supplied to the external load or circuit as electrical energy.
Wire clips
Made of plastic. Use to create experimental circuits in the laboratory. The wires with clips are used for solutions only and thus a physical entity can be dissolved in water to check electrical conductivity.
Beakers
A cylindrical glassware/plastic container with a flat bottom with capacities ranging from 1 millimeter to several litres.
Test tube
Also known culture tube or sample tube. A glassware consisting of a finger-like length of glass or clear plastic tube open on one side and rounded and closed on the other.
Usually placed in all-purpose stands.
Multimeter
Also known as multitester/ VOM. Usually can measure voltage, current and resistance.
Conical flask
A titration flask consisting of a conical body, flat bottom and cylindrical neck. Ideal for heating and mixing.
Crucible
A small cup like apparatus about the size of a shot glass made of porcelain or non-reactive material. Used to to contain chemical compounds when heated to extremely high temperature.
Spatula
Small stainless steel apparatus, spoon like curved on one end while flat like rectangular on the other end.
Used for scraping, transferring or applying powders and paste like chemicals or treatments.
Bunsen burner
A small gas burner used in the laboratory for heating combustion and sterilization.
Made up of a metal tube gas intel at the bottom of the tube.
Tripod
Three-legged platform used to support flasks and beakers. Usually made of stainless steel or aluminum for portability in the laboratory.
Wire gauze
Placed over a tripod stand to provide a flat base for glassware. The edges of the wire gauze are often turned inward.
Led bulb
Used in a circuit as a tester for electrical conductivity.
Hand gloves
To prevent burns or rashes on the skin from coming into contact with any of the chemicals.
Cork
Partially inserted in a container to form a seal.
Often made of rubber or wood.
Corks may have holes to allow for thermometers, tubes and other devices without the chemicals leaking out.
Condenser
Used to condense vapours. Used for distillation, reflux and extraction.
Apparatus parts of electrochemical cell.
2 beakers, electrodes, electrolyte, wires, Salt bridge, lamp
Apparatus set up of electrolytic cell
Battery, 1 beaker, electrodes, electrolyte, wires.
Conversion of energy in an electrolytic cell.
Electrical to chemical
Conversion of energy in an voltaic/galvanic cell.
Chemical to electrical.
Reaction in electrolytic cell
A non-spontaneous redox reaction occurs with provision of electrical energy as a catalyst.
Reaction in a voltaic or galvanic cell
Spontaneous reaction where the energy produced in the redox reaction is used to electrical energy.
Physical properties of metals (9)
Low melting point, high density, thermal and electrical conductivity, malleability, high tensile strength, solid/liquid state only, lustrous, ductile
Metal chemical properties (4)
Tendency to donate electrons
Displace hydrogen gas from dilute acids.
React with oxygen to produce ‘basic’ oxides.
React with hydrogen to produce hydrides.
Sodium and chlorine reaction setup
Rounded flask with chlorine gas and sand(to prevent apparatus breaking due to excess heat). A small tube through which a small piece of sodium and a drop of water is added to produce an orange flame and salt.
Potassium and water reaction
When the potassium is placed in water, it floats because it is less dense than the water. The hydrogen gas given off in the reaction pushes the potassium around on the surface of the water.
Potassium reacts violently with water. Enough heat is produced in the reaction to ignite the hydrogen gas given off. The hydrogen gas is contaminated with potassium which results in the lilac (bluish pink) flame.
Sodium and water reaction
Sodium and water also react vigorously. Sodium has a low melting point so the heat given off in the reaction is enough to melt the sodium and cause it to form a ball. As hydrogen is produced, it pushes the ball of sodium around on the surface of the water. Sometimes, the hydrogen can ignite and produce an orange flame due to the sodium impurities it contains.
Lithium and water reaction
When lithium reacts with water it does not produce heat quickly enough to ignite the hydrogen given off or melt the lithium, which has a higher melting point than potassium and sodium. (Colourless)
Calcium and water reaction
The calcium metal begins to bubble vigorously as it reacts with the water, producing hydrogen gas, and a cloudy white precipitate of calcium hydroxide.
Magnesium and water reaction
It is possible to create a weak reaction between very clean magnesium ribbon and cold water. However, it is likely to only result in a few bubbles of hydrogen gas as the magnesium hydroxide produced is insoluble and forms a barrier on the surface of the magnesium. This barrier prevents further reaction.
Potassium, Calcium, Sodium or Lithium reaction with steam.
If reacted potassium, sodium, lithium or calcium with steam, the resulting reaction would be so violent that the metal would explode, igniting the hydrogen in a fiery ball.
Can metals below magnesium in the reactivity series reacted with water at room temperature?
No, it requires extra energy in form of heat to react.
Reaction of metals with acids.
Group 1 metals (potassium, sodium and lithium) react violently even with dilute acids. The reaction will often produce enough heat to ignite the hydrogen gas given off.
Other metals produce less violent reactions with acids. The speed of these reactions and quantity of hydrogen produced can be used to arrange the metals in order of their reactivity, with aluminium being a notable exception.
Reaction observations of aluminum and acid.
The initial reaction seems very slow, but visibly speeds up later on.
Flame colour in Potassium salt + Oxygen, product colour
Light-purple colour. Potassium oxide is light-yellow coloured.
Flame colour in Sodium salt + Oxygen, product colour
Bright-yellow flame, Sodium oxide is white coloured.
Flame colour in Lithium salt + Oxygen, product colour
Red coloured flame, Lithium oxide is white coloured.
Flame colour in Calcium salt + Oxygen
Intense orange colour
Flame colour in Magnesium salt+ Oxygen
Exceptionally bright white flame, requires sunglasses or welding glasses as protection for eyes.
Flame colour in Aluminium salt+ Oxygen, product properties
Bright white flame, less bright than magnesium+oxygen flame. Product is white and insoluble in water.
Flame colour in Zinc salt+ Oxygen, product properties
Light blue flame, white product insoluble in water.
Flame colour in Iron + Oxygen, product properties
When iron burns it produces a bright orange flame. The iron (III) oxide produced has an orangey brown colour, while tri-iron tetroxide is dark grey or black. Iron oxide is insoluble in water.
Lead oxides.
PbO(lead monoxide yellow in colour), PbO2(Lead(IV) dioxide, brown in colour) and Pb3O4(Tri-lead trioxide, red in colour).
Copper salt+ Oxide, product properties and flame colour.
Green flame, copper(II) oxide is black and insoluble in water.
Metals that won’t react with oxygen.
Gold, Platinum and Silver (Blow copper in the reactivity series)
Tests to identify metals(5)
Flame test(Reaction with oxygen), Reaction with water, Reactivity series, Physical properties, Reaction of metals with acids.
How to identify metals with the property of relative reactivity?
A more reactive metal displaces a less reactive metal from its salt solution. Pieces of the metal are added to the aqueous salt solution while the observations are done a day later.
Forms of metal in nature (4)
Metal salts
Metal Ores
Pure metals
Minerals
Characteristics of minerals (5 answers)
Natural or synthetic State of matter Crystalline or amorphous Element, compound or mixture Organic and Inorganic
Minerals VS Ores
Naturally occuring substances of metals present in the earth’s crust are known as minerals, while minerals that can be used to profitably obtain minerals are known as ores.
Types of mining
Subsurface mining happens by digging to get the minerals while underground mining is done by making tunnels.
2 Eco-friendly methods of obtaining metals biologically.
- Farming of metals which absorb metals and are present in their sap or parts (may be genetically modified).
- Some bacteria are known to attract metals from sea-water during their metabolism, can be used to separate metals from brine.
Extraction of metals (Potassium, Sodium, Calcium, Magnesium, Aluminium)
Electrolysis
Role of metals in development
National and International industries, Imports and exports of metals, price fluctuations.
Environmental impacts due to mining/metal extractions
Mining both underground and sub-surface in forest areas destroy land which can be salvaged through land reclamation. Methods of extracting metals electrolysis (using fossil fuels to obtain electricity), burning in carbon (obtaining carbon and gases produced as by-products),, gold mining (uses mercury, lead to obtain gold as pure metal).
Ores of iron
Magnetite(up to 72.4%) and Hematite (up to 70% iron in the ore.)
Magnetite properties
Pure magnetite has 72.4% of Fe, and has the chemical formula of Fe3O4. The colour ranges from dark grey to black and is known to be magnetic which allows to differentiate this ore.
Hematite properties
Pure hematite has about 70% of hematite and is colour ranges from red to reddish brown. It has a weak magnetic property.
Common iron containing minerals
Hematite: Fe3O4 Magnetite: Fe2O3 Goethite:FeO(OH) Limonite:FeO(OH).nH2O Siderite:FeCO3
Extraction of zinc, tin, lead and iron
Through burning in carbon (All 4 elements are exactly below carbon in the reactivity series.)
Extraction of copper, mercury and silver
Through burning in air, or through self reduction.
In what form does gold and platinum occur in the ground?
Gold and silver both occur natively in the ground and are only are required to be separated from the dirt and other minerals.
How to obtain silver from silver oxide?
Heating the silver oxide to temperatures over 195 degrees celsius.
How to obtain oxides from carbonates of metal?
Calcination (Calcination is the process in which the ore of the metal is heated to high temperature in the absence or limited supply of air or oxygen.) Often it produces CO or CO2 as a by-product.
How to obtain oxides from sulphates of metals?
Roasting(Roasting is the process in which the ore is heated to high temperatures in the presence of excess supply of air or oxygen.) Often produces sulphur oxides as a by-product.
How to obtain metals from their oxides?
Displacement reaction. (Using a relatively reactive as a reductive agent, often carbon)
What similarities can be found in roasting, calcination and deoxidising a mineral?
The by-product is always a gas.
Malachite is the ore of?
Copper
Cinnabar is the ore of?
Mercury
Limestone is the ore of?
Calcium
Majority of metals ore in the forms of: ?
Sulphides, Oxides or Carbonates.
Downs cell setup
The Downs cell is used in industry to produce sodium metal. The cell consists of a central carbon anode surrounded by a cylindrical iron cathode. An iron mesh screen is used to prevent chlorine gas, formed at the anode, from coming into contact with sodium metal formed at the cathode.
The sodium metal rises in the molten mixture and is collected in a water tight storage vessel. The high current passing through the cell provides sufficient heat to keep the mixture molten. Now sodium chloride melts at approximately 800°C this requires a significant amount of energy to be supplied. Not only is the issue of viability important but at this temperature molten sodium forms a thick fog inside the reaction vessel which is difficult to recover. To lower the melting temperature, calcium chloride is added to the sodium chloride in a 1:2(NaCl:CaCl2) part mixture. The mixture has a much lower melting temperature, around 600°C which prevents the formation of the sodium fog.
Use of downs cell in the laboratory
To separate salt and obtain its elements.
Cathode and anode used in a downs cell?
Central Carbon anode surrounded by iron mesh and iron cathode.
Why is CaCl2 added to the electrolyte mixture in the downs cell?
To reduce the overall melting point of the mixture to prevent formation of fog as well as reducing the amount of energy required.
What is the thermite reaction?
An exothermic redox reaction between any metal oxide (usually iron(III) oxide) and aluminium where aluminium is oxidised when ignited.
Setup of thermite reaction in lab.
For the reaction a pot with aluminium powder and iron(III) oxide is put into a pot, with a magnesium ribbon as a fuse to ignite the mixture. The pot is suspended over another vessel as the pot may break due to the extremely endothermic reaction. Safety glasses or sunglasses is a must.
Thermite reaction chemical formula (iron III oxide)
Fe2O3 + 2Al –> Al2O3 + 2Fe
Uses of the thermite reaction
Welding and repairing railway tracks.
The oxidising agent, reducing agent, the oxidised element and the reduced element in the thermite reaction.
Aluminium is oxidised, Iron is reduced, Aluminium is the reducing agent (it reduces iron) and Iron is the oxidising agent (it oxidises aluminium)
Reduction in terms of hydrogen and oxygen
Gaining hydrogen or losing oxygen
Oxidation in terms of hydrogen and oxygen
losing hydrogen or gaining oxygen
Oxidation in terms of gain or loss of electrons
Loss of electrons
Reduction in terms of gain or loss of electrons
Gain of electrons
Oxidising agent definition and relationship with reduced/oxidised atoms.
A oxidising agent oxidises something else, for which it gains electrons and hence is reduced.
Reducing agent definition and relationship with reduced/oxidised atoms.
A reducing agent reduces something else, for which it loses electrons and hence is oxidised.
Why is carbon used in the displacement method of extraction?
Carbon is easy to obtain in larger amounts at cheaper rates, while the by-product carbon dioxide is a gas which makes it easier to separate the by-products of the reaction without any further efforts.
What test is to be done to check the presence of carbon dioxide as a by-product in the displacement method of extraction?
Lime water test, by placing two stands, 1 that is being heated and the other with lime water on two different stands and joining them together with corks and a pipe.
Why are highly reactive metals not extracted through displacement?
Highly reactive metals above the carbon in the reactivity series are hard to obtain in their pure state in large amounts (aluminium may not be a good choice as it has almost no metals between C and Al), thus is not suitable to be done through the displacement reaction.
Are metals obtained through displacement and electrolysis methods pure?
While those obtained through electrolysis are pure, it requires refining to get pure metals in reduction and self-reduction processes.
What is self reduction?
It is an extraction process through which metal compounds are heated themselves which results in reduction of the compound to produce a metal and a by-product.
Which metals are extracted through self reduction?
Hg, Cu, Pb, Sb
Give the reaction of copper self-reduction.
2Cu2S + 3O2 ——> 2Cu2O + SO2
2Cu2O + Cu2S —> 6Cu + SO2
Rules for assigning oxidation number.
The oxidation number of any lone element is 0. For example, H2, Mg
Oxidation number is always assigned to the most electronegative element first
The net charge of any molecule is 0, i.e., the negative and positive of each element cancel out each other.
Standard alkaline battery components
Carbon rod(negative terminal), zinc (positive terminal), manganese(IV) oxide(electrolyte).
What are the components of a lithium ion battery?
Copper sheet (negative tab), Aluminium sheet (positive tab), lithium compound(smeared on aluminium), graphite (smeared on copper), electrolyte(organic solvent), separator in the middle of the electrolyte( to prevent a short circuit if the electrolyte dries up).
What is the direction of ions when a lithium ion battery is charged?
The electrons are stored in the graphite through the wire, while the lithium is separated from the compound and passes through the electrolyte to reach the graphite as well.
What is the direction of ions when a lithium ion battery is discharged?
The electrons move through the wire back to the aluminium sheet smeared with the lithium compound while the lithium element passes through the electrolyte back to the lithium compound.
What is the setup of a usual electrochemical cell?
Two beakers with electrolytes, two electrodes in each beaker connected by a wire, a salt bridge in the middle with a mixture of agar-agar jelly and a salt.
What is the reaction occuring in an electrochemical cell, with beaker A filled with Zinc Sulphate and Zinc anode, and beaker B filled with Copper Sulphate and copper cathode?
Zn –> Zn2+ + 2e-
Cu + 2e- –> Cu2+
OR
Zn + Cu2+ —> Zn2+ + Cu
What is the use of the salt bridge in an electrochemical cell?
In the anode beaker where the excess positive ions are released and the cathode where the excess negative ions are remaining after positive electrons are absorbed, the ions from the salt bridge are discharged into each solution to balance these charges. (Some of the ions present excessively in the solution may also enter the salt bridge)
In a galvanic or electrochemical cell, what is a half cell?
A single beaker with an anode/cathode in it, with a proper setup is known as a half cell.
What would happen if there is no salt bridge?
The charges will accumulate in the beaker solution, and cause the flow of charges to halt, more like an incomplete circuit.
When does an irreversible electrochemical cell stop working?
When one of the electrode is completely diffused.
Which electrode is thickened in an electrochemical cell?
The cathode(copper)
Metals required by the human body in high amounts
macrometals (Sodium, potassium, calcium and magnesium)
Metals required by the human body in lower amounts
micrometals (Iron, Zinc, Copper, selenium, manganese, chromium, cobalt, Iodine)
Metals harmful for consumption (Any 5)
Mercury, Lead, Arsenic, Cadmium, Thallium, Beryllium.
What is bioaccumalation?
When some harmful substances are consumed by organisms at the bottom of the food chain, it may accumulate in higher amounts in animals much higher in the food chain in comparison and may be harmful to such organisms.
What methods can be used to prevent corrosion?
Painting, Alloying, Electroplating, Greasing
3 types of alloy
Substitutional alloy, Interstitial alloy, Alloy with both substitutional and interstitial properties.
What is the usual melting temperature of a fusible metal/alloy?
Below or around 300/450 degrees fahrenheit (different websites have different values)
What is a shape memory alloy?
An alloy that retains it previous shape on heating or giving pressure is known as a shape memory alloy.
Landolt’s tube
An H-shaped tube, that is used mainly for the check of conservation of mass. Reactant liquids are added to both sides of the tubes, in amounts that do reach up to the horizontal connection between the tubes, after which the apparatus is sealed and shaked or tilted for the reaction. There are better methods, but this was used initially for finding the law of conservation of mass.
