Chemical elements

Question 1

Chemical Element

Answer 1

substance whose atoms all have the same number of protons
all of a particular element’s atoms have the same atomic number.

Question 2

Chemical properties of elements

Answer 2

Density
Melting point
Boiling point
Molecule Types

Question 3

Density

Answer 3

ratio of the mass of an object to its volume
physical property used to describe how tightly packed the molecules are in an object
d = M/V
commonly expressed in units of grams per cubic centimetre g/cm3 or g/ml
temperature goes down, the density usually becomes greater

Question 4

Covalent compounds + boiling points

Answer 4

Acetone 56-57°C
Benzene 78-80°C
Chloroform 60-62°C
Ethyl alcohol 78°C
Carbon tetrachloride 76.7°C

Question 5

Ionic Compounds + boiling points

Answer 5

Water 100°C
Nitric acid ~83°C
10% NaCl solution in water ~100.5°C

Question 6

ionic compounds bp compared to covalent compounds bp

Answer 6

higher
due to the presence of ionic bonds in ionic compounds

Question 7

boiling points of ethanol and methoxymethane

Answer 7

ethanol (with hydrogen bonding) 78.5°C
methoxymethane (without hydrogen
bonding) -24.8°C

Question 8

branching in the molecule bp effect

Answer 8

van der Waals attractions less effective = lower

Question 9

Na + O: observation, order of reactivity, product

Answer 9

Burns quickly with a bright yellow flame
1st - most reactive
Na2O, sodium peroxide - a yellow powder

Question 10

Mg + O: observation, order of reactivity, product

Answer 10

Burns with a brilliant white flame
2nd.
MgO, magnesium oxide - a white ash.

Question 11

Fe + O: observation, order of reactivity, product

Answer 11

Does not burn. Hot metal glows in oxygen and gives off yellow sparks.
3rd.
Fe203, iron oxide - an orange powder.

Question 12

Cu + O: observation, order of reactivity, product

Answer 12

Does not burn. Metal eventually coats with a black layer.
4th - least reactive.
CuO, copper oxide - a black powder

Question 13

K + H2O: observation, order of reactivity, product

Answer 13

Violent reaction with cold water. Floats and catches fire.
1st - most reactive.
Potassium hydroxide, KOH and hydrogen gas.

Question 14

Na + H2O: observation, order of reactivity, product

Answer 14

Very vigorous reaction with cold water. Floats. Can be lit with a lighted splint.
2nd.
Sodium hydroxide, NaOH and hydrogen gas.

Question 15

Ca + H2O: observation, order of reactivity, product

Answer 15

Less vigorous with cold water. 3rd.
Calcium hydroxide, Ca(OH)2 and hydrogen gas.

Question 16

Mg + H2O: observation, order of reactivity, product

Answer 16

Very slow with cold water, but vigorous with steam.
4th.
Magnesium oxide, MgO and hydrogen gas.

Question 17

Zn + H2O: observation, order of reactivity, product

Answer 17

Quite slow with steam.
5th.
Zinc oxide, ZnO and hydrogen gas

Question 18

Fe + H2O: observation, order of reactivity, product

Answer 18

Slow with steam.
6th.
Iron oxide, Fe203 and hydrogen gas.

Question 19

Cu + H2O: observation, order of reactivity, product

Answer 19

No reaction with steam.
7th - least reactive.

Question 20

Mg + HCl: observation, order of reactivity, product

Answer 20

Vigorously reacts with a stream of gas evolving.
1st - most reactive.
Magnesium chloride, MgCl2 and hydrogen gas.

Question 21

Zn + HCl: observation, order of reactivity, product

Answer 21

Quite slow reaction with a steady stream of gas evolving.
2nd.
Zinc chloride, ZnCl2 and hydrogen gas.

Question 22

Fe + HCl: observation, order of reactivity, product

Answer 22

Slow reaction with a gentle stream of gas evolving.
3rd.
Iron chloride, FeCl2 and hydrogen gas.

Question 23

Pb + HCl: observation, order of reactivity, product

Answer 23

Very slow and acid must be concentrated.
4th.
Lead chloride, PbCl2 and hydrogen gas.

Question 24

Cu + HCl: observation, order of reactivity, product

Answer 24

No reaction.
5th - least reactive.

Question 25

metals + hydrogen

Answer 25

metal hydrides
Hydrogen gas is passed over heated sodium, then sodium hydride is formed.

Question 26

Acids and bases react with most metals to form

Answer 26

salt and hydrogen gas
more active than acid or base can undergo a single displacement reaction

Question 27

What Causes Acid Rain?

Answer 27

non-metallic oxides - sulfur dioxide (SO2) and
nitrogen oxides (NOX) are emitted into the atmosphere and transported by wind and air currents.
SO2 and NOX react with water, oxygen and other chemicals to form sulfuric and nitric acids.
These then mix with water and other materials before falling to the ground.
While a small portion of the SO2 and NOX that cause acid rain is from natural sources such as volcanoes, most of it comes from the burning of fossil fuels.

Question 28

Chemical properties of non-metal

Answer 28

• Non metallic oxides are acidic in nature.
• They do not dissolve in dilute mineral acids.
• They form stable compounds with hydrogen.
• Their chlorides are completely hydrolyzed by water.

Question 29

non-metals with oxygen

Answer 29

form acidic oxides or neutral oxides

Question 30

non-metals with water

Answer 30

do not react with water (steam) to evolve hydrogen gas

Question 31

non-metal with acids

Answer 31

do not react with acids because they are negatively charged electrons.

Question 32

non-metal with salt solution

Answer 32

do not react with salt solution but displace less reactive non-metal from the salt

Question 33

non-metal with chlorine

Answer 33

form covalent chlorides which are non - electrolytes

Question 34

A Binary Compound

Answer 34

formed from two types of elements
Metal + Metal = Metallic Compound
Metal + Non-Metal = Ionic compound
Non-Metal + Non-Metal = Covalent compound