Chapter 17 Electron Transfer and Corrosion

Question 0

name the two main sources of ions in oceans

Answer 0

leeching of minerals from rocks and soil by rainwater and hydrothermal vents in mid- ocean ridges

Question 1

what are the main ions causing salinity in oceans

Answer 1

magnesium, calcium, potassium, sulphate, hydrogen carbonate and bromide ions as well as chlorine and sodium.

Question 2

define Aquifer

Answer 2

a subterranean source of water

Question 3

explain why the presence of natural acids in soil and water accelerates the leeching process

Answer 3

the acids react with the substances in the soil to ionise them which then is attracted to the water due to its polar nature.

Question 4

define Leeching

Answer 4

the removal of soluble materials by water as it percolates through a structure

Question 5

equations for equilibrium associated with carbonic acid ionisation

Answer 5

CaCO3(s) + 2H2O(l) –> Ca(2+)+ 2H2O(l) + CO2(g)

H2CO3 + H2O(l) H3O(+) + HCO3(-)

Question 6

when were the first signs of hydrothermal vents discovered and where

Answer 6

1972 from the ocean floor near the galapagos rift in the pacific ocean

Question 7

how does a hydrothermal vent spread ions?

Answer 7

The superheated water (360 C) leeches the minerals from the surrounding rock. The hot water dissolves minerals that wouldn’t normally dissolve and as it spreads out cools and deposits the now insoluble ions. The soluble ions are suspended in the water and are spread with the ocean currents

Question 8

define corrosion

Answer 8

corrosion is the chemical attack on a metal by the environment.

Question 9

chemical formula for rust

Answer 9

Fe2O3.(x)H20

where x is less than 3

Question 10

observations of rust

Answer 10

both water and oxygen are present
salt water accelerates the process
impure iron rusts faster than pure iron
iron rusts more rapidly when it is attached to a less reactive metal
rust occurs more rapidly where the iron is under mechanical stress.

Question 11

state the equations associated with rusting:
A)oxidation half equation at the anodic site
B)reduction half equation at cathodic site
C)full equation
D)rust reaction

Answer 11

A) Fe(s)–> Fe(2+) + 2e-

B) O2(g) + 2H2O(l)+ 4e- –> 4OH-

C) 2Fe(s) + O2(g) + 2H2O(l) —> 2Fe(OH)2(s)

D1) 4Fe(OH)2(s) + O2(g) + 2H2O(l) —> 4Fe(OH)3(s)

D2) 2Fe(OH)3(s) —> Fe2O3.H2O(s) + 2H2O(l)