U2 AOS 1 Chapter 10 C, D & E

Question 1

acidic solution

Answer 1

greater concentration of hydronium ions than hydroxide ions

Question 2

basic solution

Answer 2

greater concentration of hydroxide ions than hydronium ions

Question 3

ionic product of water definition

Answer 3

Kw, concentration of ions present in water at 25degrees celcius

Question 3

autoionisation

Answer 3

process where an atom or molecule spontaneously forms ions

Question 4

neutral solution

Answer 4

equal concentration of hydroxide and hydronium ions

Question 5

pH

Answer 5

concentration of hydronium ions in a solution

Question 5

What happens if the temp and Kw value increases?

Answer 5

The concentration of hydronium ions would increase, pH decreases

Question 5

ionic product (kw) of water value

Answer 5

Kw = 1.00 x 10^-14M^2 (found by multiplying [H3O+] & [OH-]

Question 6

calculating pH (formula)

Answer 6

pH=-log[H3O+] OR [H3O+] = 10^-pH

Question 6

limitations of the pH scale

Answer 6

only works for aqueous solutions

Values only valid at 25oC (298 K)

goes beyond typical range of 0 - 14

can only be readily calculated with strong acids/bases

Question 7

natural indicator

Answer 7

an indicator made from naturally sourced substances eg. litmus paper

Question 7

ph meter

Answer 7

instrument used to measure the pH of a solution through quantitative, specific measurement of difference of electrical potential

Question 7

Why can we calculate the pH of 1.00M HCl but not 1.00M CH3COOH?

Answer 7

HCl = strong acid, CH3COOH = weak acid, only in HCl [H3O+] = [HCl], in CH3COOH, concentration of hydronium cannot be determined from this info alone as it does not completely ionise.

Question 8

meters vs indicators

Answer 8

meter: quantitative, specific and highly accuracy, reproducible - no change between measurements

indicator: qualitatitive, approximated range of values - low accuracy, if true pH is on border if colour range, pH may differ greatly between trials

Question 8

indicator

Answer 8

a substance that changes colour to indicate pH range

Question 8

commercial indicator

Answer 8

an artificially prepared indicator

Question 9

combustion

Answer 9

fuel reacts w/ oxygen (burning)

Question 10

calcification

Answer 10

chemical process that forms calcium carbonate (CaCO3)

Question 11

decalcification

Answer 11

chemical process that breaks down calcium carbonate

Question 12

carbonic acid definition

Answer 12

formed by reaction of CO2 with H2O

Question 12

nitric acid definition

Answer 12

formed through a series of reactions in the atmosphere between nitrogen gas, oxygen gas and water

Question 13

sulfuric acid definition

Answer 13

formed through a series of reactions in the atmosphere between sulfur, oxygen gas and water

Question 14

normal rain acidity

Answer 14

acidic (5/6) due to dissolved CO2 creating carbonic acid

Question 15

acid rain

Answer 15

rain containing nitric and sulfuric acids eg. CO2(g) + H2O (l) <-> H2CO3 (aq) <-> H+ (aq) + HCO3- (aq)

Question 16

sulfuric acid formation

Answer 16

formation of dilute sulfuric acid through sulfur (in fossil fuels) given energy through combusion

Question 17

sulfuric acid formation equation

Answer 17

2SO2(g) + O2(g) + 2H2O(l) <-> 2H2SO4(aq)

Question 18

nitric acid formation

Answer 18

through fossil fuel combustion nitrogen gas reacts to form nitrogen oxide compounds (NOx) ie nitrogen monoxide (NO) or nitrogen dioxide (NO2)

Question 19

nitric acid formation equation

Answer 19

1. 2N2(g) + 5O2(g) + 2H2O(l) <-> 4HNO3(aq)

Question 20

effects of acid rain (other than plants)

Answer 20

1. runoff causes lake acidification - lowers pH, harms/kills aquatic life 2. reactions w/ weather exposed metals 3. reactions w/ limestone (CaCO3, readily reacts) i. CaCO3(s) + H2SO4(aq) -> CaSO4(aq) + CO2(g) + H2O(l) ii. CaCO3(s) + 2HNO3(aq) -> Ca(NO3)2(aq) + CO2(g) + H2O(l)

Question 20

effects of acid rain on plants

Answer 20

1. toxic aluminium ions are absorbed = death Al(OH)3(s) + 3H+(aq) <-> Al3+(aq) + 3H2O(l) 2. H+ ions cause essential growth ions (Ca2+, K+, Mg2+) to be released and washed away 3. damage to waxy layer on leaves = death

Question 21

ocean acidification

Answer 21

accelerated absorption of CO2 by oceans, H+ ions are formed, carbonic acid (H2CO3) formed, pH decreases

Question 22

effects of ocean acidification

Answer 22

CaCO3 of marine invertebrates' exoskeletons react w/ acidity = unable to grow/shells slowly dissolve

Question 23

why can oceans change in acidity over time?

Answer 23

due to reversible nature of some chemical reactions

Question 24

carbonic acid formation equation

Answer 24

CO2(g) + H2O(l) <-> H2CO3(aq)

Question 25

What is the equation for producing Al+ which harms plants?

Answer 25

Al(OH)3(s) + 3H+(aq) <-> Al3+(aq) + 3H2O(l)

Question 26

strength vs pH

Answer 26

strength = no of ions, pH = [H3O+] therefore, higher strength of a base generally means higher number of OH- ions and a higher pH higher strength of an acid generally means higher number of H3O+ ions and a lower pH