y11 chem 100 questions

List the three states of matter in increasing order of particle energy

Solid liquid gas

In which two states can diffusion occur?

Liquid and Gas

How could you confirm whether a substance is pure or impure?

Measure its melting or boiling point. Pure substances have fixed, sharp melting/boiling points

Give the lowest and highest possible values for any Rf value

0.00 and 1.00

Why do atoms have no overall charge?

They have equal numbers of protons and electrons

Define the term ‘isotopes’

Atoms with the same number of protons but with different numbers of neutrons

Give the period number of the atom with electron configuration 2,8,7

3

Why are the elements in group 0 (noble gases) generally unreactive?

They have a full shell of outer electrons

Complete the word equation: sodium + water —>

Sodium Hydroxide + Hydrogen

Give another term for a displacement reaction

A redox reaction

Steel dustbins can be sprayed with zinc to prevent them from rusting. What name is given to this method of rust protection?

Galvanising

Complete the word equation: Chlorine + Potassium Iodide —>

Potassium chloride + Iodine

Nitrogen is the most abundant gas in the air. What is the percentage of nitrogen in air?

78%

Name the third most abundant gas in air

Argon

A gas syringe contains 100 cm (cubed) of air. If all of the oxygen was removed from the syringe, how much gas would remain in the syringe?

79cm(cubed)

Name one type of reaction which removes oxygen from the air.

Rusting, combustion/burning

Some sulfur is burnt in a gas jar of oxygen. Water is then added to the jar, followed by universal indicator. What colour will the universal indicator turn?

Red

Name the two products formed when copper carbonate is heated

Copper oxide and carbon dioxide

Name the type of reaction which takes place when copper carbonate is heated

Thermal decompostion

Carbon dioxide is a greenhouse gas which contributes to global warming. True or False?

True

Carbon dioxide causes damage to the ozone layer in the stratosphere. True or False?

False

Ionic bonding is the electrostatic attraction between…

…oppositely charged ions

When a metal atom loses electron(s), it forms an ion with a …. Charge(positive or negative)

Positive

When a metal atom loses electron(s) to form an ion, is it being oxidised or reduced?

Oxidised

Give the formula of a magnesium ion

Mg(2+)

Give the formula of an oxide ion

O(2-)

Give the formula of sulfide ion

S(2-)

Give the formula of a sulfate ion

SO4(2-)

Give the formula of an ammonium ion

NH4(+)

Give the formula of a hydroxide ion

OH(-)

Describe the melting points of most ionic compounds

high

Describe the conductivity of ionic compounds

Conduct only when molten or dissolved in water

Covalent bonding is the electrostatic attraction between…

…a shared pair of electrons and the nuclei of the two atoms involved

Which of the following may enable a compound to conduct electricity? (i) ions which can move (ii) molecules which can move (iii) delocalised electrons

(i) and (iii) only

Name a non-metal structure which contains delocalised electrons

Graphite

What is meant by the term ‘double covalent bond’

A bond where each atom is sharing two electrons (compared to sharing one each in a single bond)

Give the formula of hydrogen chloride gas

HCI

Give the formula of ammonia gas

NH3

Give the formula of methane gas

CH4

Give two examples of giant covalent structures

Diamond, graphite, sand

Describe the melting points in simple molecular structures

Low

Describe the melting points in giant covalent structures

High

Which of the following have weak intermolecular forces giving rise to a low melting point? (i) methane (ii) graphite (iii) sodium chloride

(i) only; intermolecular forces only exist in simple molecular structures

Describe the structural feature in graphite which makes it useful in pencils

It is formed in layers which can slide over each other

Give the equation for calculating the rate of a chemical

Amount of chemical (made or used up) divided by the time taken

Give two possible units for reaction rate

G/s or cm(cubed)/s

Describe two possible ways of measuring the volume of gas given off during a reaction

(i) Collect the gas in a gas syringe or(ii) use an inverted measuring cylinder filled with water

A student plots a graph of volume of gas made against time. What feature of the graph tells us the reaction rate.

The gradient

Describe the effect of decreasing the particle size of a solid reactant on the rate of reaction

The rate will increase (the reaction gets faster)

Explain the effect of decreasing the particle size of a solid reactant on the rate of reaction.

Smaller particles have a bigger surface area so more particles available to react, so more frequent collisons.

Covalent bonding takes place between a metal atom and a non metal atom. True or false?

False. Covalent bonding takes place between non-metal atoms only

Describe the effect of increasing reactant concentration on the rate of reaction

The rate will increase (the reaction gets faster)

Explain the effect of increasing reactant concentration on the rate of reaction

More reactant particles in the same volume results in more frequent collisions

Describe the effect of increasing temperature on the rate of reaction

The reaction gets faster

Explain the effect of increasing temperature on the rate of reaction

Reacting particles gain energy resulting in (i) more frequent collisions and (ii) more collisions greater than the activation energy

What is a catalyst?

A substance which speeds up a reaction but which is not used up during the reaction

How does a catalyst work?

It provides an alternative reaction pathway with a lower activation energy

Name the process by which crude oil is refined into useful substances

Fractional distillation

Name the fraction which is released from the top of the fractionating column

Refinery gases

Name the fraction which is released from the second highest point on the fractionating column

Gasoline (petrol)

Name the fraction formed at the bottom of the fractionating column

Bitumen

Give the meaning of the term ‘hydrocarbon’

A compound formed from carbon and hydrogen only

Name the products formed when a fuel undergoes incomplete combustion

Carbon monoxide/ carbon and water

Name the products formed when a fuel undergoes complete combustion

Carbon dioxide and water

Give the general formula of the alkanes

CnH2n+2

Name the first five alkanes

Methane, ethane, propane, butane, pentane

Name the type of reaction which takes place when an alkane reacts with bromine

Substitution

Give the meaning of the term ‘displayed formula’

A representation of a chemical formula which shows the arrangement of every atom and every bond in a molecule

Explain the term ‘isomers’

Molecules with the same molecular formula but different displayed formulae

Apart from the reacting chemicals, what else is needed for an alkane to react with bromine

UV light

State the conditions needed for a longer chain hydrocarbon to undergo cracking

Heat to 650 degrees celsius; aluminium oxide/alumina catalyst

Why is cracking important

It produces (i) shorter chain alkanes which are in high demand as fuels and (ii) alkenes which are used to make polymers

Give the general formula of the alkenes

CnH2n

What is the feature found in alkene molecules but not alkane molecules

A C=C double bond

Describe the chemical test for an alkene

Add orange bromine water which will turn colourless if an alkene is present

Name the type of reaction which takes place when an alkene reacts with bromine

Addition

Give the meaning of the term ‘polymer’

A long chain molecule formed when many when many smaller molecules combine

Give the meaning of the term ‘monomer’

A single small molecule that combines with others to form a polymer

Name the polymer formed when chloroethene undergoes polymerisation

Poly(chloroethene)

Give the meaning of the term ‘repeat unit’

A small length of a polymer chain, formed from one monomer molecule

Give two problems caused by the disposal of polymers

(i) they take up landfill space for many years without biodegrading and (ii) they emit toxic gases when burnt

How many elements are there in the compound NaHCO3

4

How many atoms are there in one molecule of C3H6Br2

11

Explain the meaning of the term ‘relative formula mass’

The sum of the relative atomic masses of every atom in a chemical formula

Calculate the realtive formula mass of C4H10 (C=12; H=1)

58

Calculate the relative formula mass of Na2SO4 (Na=23; S=32)

142

Calculate the percentage by mass of sodium in sodium in sodium chloride, NaCl (Na= 23 Cl= 35.5)

23/58.5 x 100=39.3%

How many atoms are found in one mole?

6 × 10(23 at the top)

Give the equation that links number of moles with mass and relative formula mass

Moles = mass/Mr

How many moles of carbon dioxide are found in 176g

176/44 =4

Give the meaning of the term molecular formula

An expression which gives the exact numbers of atoms of each element in one molecule of a substance

Give the meaning of the term empirical formula

The simplest ratio of the numbers of each element in a chemical formula

Give the empirical formula of butane,

C4H10

What is a limiting reactant?

The reactant that runs out in a reaction before any of the other reactants have been used up

When a metal burns in air, why does the mass increase?

Because oxygen atoms from the air have combined with the metal

What is the law of conservation of mass?

That atoms are not created or destroyed during a reaction

Give the state symbol for gas

(g)

Give the state symbol for a substance dissolved in water

(aq)

Give the value of X in the equation:  CH4  + 2O2  -->  CO2  +  XH2O

2

Give the value of Y in the equation:  C3H8  + YO2  -->  3CO2  +  4H2O

5