Bonding, Structure, and The Properties of Matter (exam qus)

Describe a method the student could use to compare the reactivity of metal Q with that of zinc. Your method should give valid results.

• measure temperature change

• when each metal is added to silver nitrate

• same concentration/volume of solution

• the greater the temperature change, the more reactive

explain why graphite is:

• a good electrical conductor

• soft and slippert

• bonds are covalent

• giant structure

• three covalent bond per carbon atom so one electron per carbon is delocalised

• these delocalised electrons can move through the structure carrying electrical charge so graphite conducts electricity

• layered structure of hexagonal rings with weak intermolecular forces between layers

• so the layers can slide over each other so graphite is soft and slippery

Explain how a covalent bond holds two atoms together.

electrostatic force of attraction between shared pair of negatively charged electrons and both positively charged nuclei

Compare the bonding within the chains with the forces between the chains in this polymer.

• covalent bonds between atoms in the chain

• intermolecular forces between the chains

• covalent bonds are strong

• intermolecular forces are weak

 Suggest one property that makes the carbon molecule in Figure 1 useful in nanotechnology.

• conducts heat

• conducts electricity

Name the type of carbon molecule in Figure 1.

fullerene

Suggest how anhydrous copper sulfate is used to test for water

Turns white to blue

Describe how copper sulfate solution is obtained from the plants used in phytomining

• burned to produce ash

• Copper compounds in ash dissolved in sulfuric acid

Compare phytomining and bioleaching

• Bio leaching is very slow but although slow, phytomining can be made more efficient by growing quick growing plants

• Bioleaching extracts copper from quarrying waste but phytomining extracts copper from contaminated ground

• Phytomining decontaminates polluted ground but bioleaching can produce toxic run off which may go into rivers

• Phytomining takes a long time to stop

• Bioleaching is a very slow process

• Plants are burned in phytomining

Emissions from car contain co2.

Explain why co2 emissions during the use and operation are not the total carbon footprint for a car.

Refer to LCA

• extracting raw materials

• Disposal at the end of life

• Manufacturing

Compare the bonding within the chains with the forces between the chains in this polymer

• bonding within the chains are covalent and are strong

• Forces between the chains are intermolecular and weak

Suggest one property that makes the carbon molecule in figure 1 useful in nanotechnology

• conducts heat

• Conducts electricity

Name the type of carbon molecule in figure 1

Fullerene

Explain why graphite is:

* a good electrical conductor
* soft and slippery

You should answer in terms of structure and bonding.

* bonds are covalent
* giant structure

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a good electrical conductor

* only 3 electrons per carbon atom used in bonds so one is delocalised
* these delocalised electrons can move through the structure carrying electrical charge
* so graphite conducts electricity

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soft and slippery

* layered structure of hexagonal rings with weak intermolecular forces between layers
* there are no bonds between the layers so the layers can slide over each other
* so graphite is soft and slippery

Give two observations you could make when a small piece of potassium is added to water.

effervescent and lilac flame

Explain why the reactivity of elements changes going down Group 1.

* reactivity increases going down the group
* outer shell is further from the nucleus
* there is less attraction between the nucleus and the outer shell
* the atom is able to lose an electron more easily

Explain why sodium oxide has a high melting point.

* giant structure
* with strong electrostatic forces of attraction between ions
* therefore large amounts of energy are needed to break the bonds

Compare the structure and bonding of the three compounds:

* carbon dioxide
* magnesium oxide
* silicon dioxide.

* silicon dioxide and magnesium oxide are giant structures
* carbon dioxide is small molecules with weak intermolecular forces

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* all 3 compounds have strong bonds
* co2 and sio2 are formed from 2 non metals and therefore are covalent
* so electrons are shared
* mgo is formed with a metal and a nonmetal so bonds in mgo are ionic
* so electrons are transferred from mg to o (2 electrons transferred)

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* bonds in sio2 are single bonds where each silicon forms 4 bonds and each oxygen form 2 bonds
* in co2 the bonds are double bonds where carbon forms 2 double bonds and oxygen forms one double bond

Explain why nitrogen is a gas at room temperature.

Answer in terms of nitrogen’s structure.

* there are weak intermolecular forces which need little energy to overcome

Silver nanoparticles are sometimes used in socks to prevent foot odour.

Suggest why it is cheaper to use nanoparticles of silver rather than coarse particles of silver.

* nanoparticles have a larger sa to v ratio so less can be used for the same effect

 Explain why iodine has a low melting point.

* simple molecules with weak intermolecular forces which require little energy to overcome

Silicon dioxide has a very high melting point.

Other substances are added to silicon dioxide to make glass. Glass melts at a lower temperature than silicon dioxide.

Suggest why.

weaker bonds

Describe the structure of a metal.

* layers of positive ions with delocalised electrons

Describe, in terms of electrons, what happens when magnesium reacts with iodine.

* magnesium loses 2 electrons
* iodine gains 1 electron

Explain why a high temperature is needed to melt potassium iodide.

* forces of attraction are strong because oppositely charged ions attract in giant structure

Evaluate the use of the materials to make badminton racket frames.

* wood is the least dense so lightest to use
* aluminium is the most dense so it will make the racket heavy
* carbon nanotube is the strongest so less likely to break
* wood and aluminium are too weak so they will break more easily
* carbon nanotube is the stiffest so least likely to bend out of shape
* wood and aluminium are not very stiff so could bend out of shape

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conclusion

Calculate the simplest whole number ratio of:

moles of iron atoms : moles of chlorine atoms

Determine the balanced equation for the reaction.

Relative atomic masses (Ar): Cl = 35.5 Fe = 56

* 4.4g of iron and 8.52g of chlorine
* iron moles = 4.48/56 = 0.08
* chlorine moles = 8.52/35.5 = 0.24
* 0.08:0.24 = 1:3

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2Fe + 3Cl2 → 2FeCl3

A student wants to compare the reactivity of an unknown metal, Q, with that of zinc.

Both metals are more reactive than silver.

The student is provided with:

• silver nitrate solution

• metal Q powder

• zinc powder

• a thermometer

• normal laboratory equipment.

No other chemicals are available.

Describe a method the student could use to compare the reactivity of metal Q with that of zinc.

Your method should give valid results.

* measure temperature change when each metal is added to silver nitrate solution
* make sure there is the same concentration of solution and mass of the metal
* the greater the temperature change, the more reactive the metal is

Describe a method for making pure crystals of magnesium chloride from magnesium and dilute hydrochloric acid.

In your method you should name the apparatus you will use.

You do not need to mention safety.

* HCl in a beaker and add small pieces of mg ribbon until magnesium is in excess
* filter excess mg using filter paper and funnel
* pour solution into evaporating basin
* heat using bunsen burner
* leave to crystallise and pat dry afterwards

Describe a safe method for making pure crystals of copper sulfate from copper carbonate and dilute sulfuric acid.

Use the information in the figure above to help you.

In your method you should name all of the apparatus you will use.

* sulfuric acid in beaker and add copper carbonate one spatula at a time
* add until copper carbonate is in excess
* filter the excess carbon carbonate using filter paper and funnel
* pour solution into evaporating dish
* heat using bunsen burner
* leave to crystallise and pat dry
* wear safety goggles

“The more energy levels (shells) of electrons an atom has, the weaker the covalent bonds that it forms.”

Use the above statement to predict and explain how the overall energy change for the reaction of ethene with chlorine will differ from the overall energy change for the reaction of ethene with bromine.

* chlorine atoms have fewer electron shells
* Cl-Cl and C-Cl bonds are stronger then C-Br bonds and Br-Br bonds

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* more energy is required to break bonds with chlorine
* more energy is given out when making bonds with chlorine

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* if Cl-Cl bond changes more, then less exothermic
* if C-Cl bond changes more then more exothermic
* can’t tell how overall energy change will differ as we do not know which changes more

Why does manganese oxide conduct electricity as a liquid?

Ions move around in the liquid

Describe what happens when a lithium atom reacts with a chlorine atom. Answer in terms of electrons.

• lithium loses one electron

• chlorine gains one electron

• transfer of one electron to form positive and negative ions

The relative formula mass (Mr), in grams, of sodium fluoride is one _______________ of the substance.

mole

one advantage of using nanoparticles in sun creams

better coverage

disadvantage of using nanoparticles in sun creams

potential cell damage