Chapter 4

Chemical Reaction

& Recycling

재활용과 화학수학

Topics

• Balanced Chemical Equations

• Stoichiometry

• Formula Mass

• Avogadro’s Number, 6.02x1023

• Molar Mass

닫힌 계 - 지구

System & surroundings

• 계와 환경– matter flow & energy flow

• open system 열린 계– matter & energy flow YES ; 비이커

• closed system 닫힌 계– matter NO & energy YES

• isolated system 고립 계– matter & energy NO ; 보온병

• 인간은 죽으나 탄소는 그렇지 않다 . 인간의 죽음과 함께 탄소의 운명이 끝나는 것이 아니다 . 탄소는 흙으로 돌아가서 , 식물이 언젠가는 다시 그 탄소를 섭취하고 , 다시 식물과 동물의 삶의 순환과정으로 유입된다 .– Jacob Bronowski

Chemical Reactions

• Respiration 호흡– 탄수화물의 일종인 글루코오스의 산화– 광합성의 역반응– C6H12O6 + O2 CO2 + H2O + Energy

글루코오스 이산화탄소 + 물

– a C6H12O6 + b O2 c CO2 + d H2O

반응물 생성물

Chemical Reactions

• Respiration– C6H12O6 + O2 CO2 + H2O + Energy

– a C6H12O6 + b O2 c CO2 + d H2O

– 1 C6H12O6 + 6 O2 6 CO2 + 6 H2O

• 모든 문명국들은 식량이 없어 극심한 위기에 놓여 있습니다 . … 이 고통 받는 사회를 구해야 할 이들은 바로 화학자들입니다 . 연구를 통해 언젠가는 지금의 기근을 풍족함으로 전환할 수 있을 것입니다 . … 여기 희미한 불빛이 보입니다 . 대기중의 질소를 비료로 바꾸는 방법은 화학자들의 위대한 발명 중 하나가 될 것입니다 .– Sir William Crookes (1898)

• 인구는 최근 200 년 동안 5 배 이상 증가하였고 , 평균 수명도 2 배 이상 늘어났다 . - 농약과 비료 , 항생제 같은 화학물질을 만들어 낼 수 있었기 때문이다 .

• 오늘날 중부 유럽에서는 1 ha 의 땅에서 약 4 톤의 농작물을 생산한다고 한다 . 화학비료가 없었던 때에는 풍년인 해에도 같은 면적에서 2 톤 이상을 생산하지 못했다 .

Chemical Reactions

• Haber-Bosch Process for Ammonia (1905)– H2 + N2 NH3

– 3 H2 + N2 2 NH3

• Changes in reaction conditions affect outcome of a reaction

• Commercial reaction are optimized for products and cost

Chemical Reactions• Ozone to Oxygen

– 2 O3 3 O2

– 중간 화학종 intermediate species

O3 O2 + O

O + O3 2 O2

O + 2 O3 3 O2 + O

알루미늄의 재활용• 알루미늄

– 3A– 자연계에서 보크사이트

• Hall-Heroult process

Chemical Reactions

• Balancing Reactions– balance metals and semi-metals first– balance heavy non-metals and halogens– balance C, N, O, H last

Al2O3 + C Al + CO2

2 Al2O3 + 3 C 4 Al + 3 CO2

Stoichiometry

• 화학양론– 화학과정에서 사용되거나 생성된 물질의

상대적 양을 결정하는 학문– 2 Al2O3 + 3 C 4 Al + 3 CO2

• Answers Questions– 알루미늄 깡통 한 개를 만들기 위해서

얼마만큼의 Al2O3 과 에너지가 필요한가 ?

– 천연 가스 1 몰이 타면 얼마만큼의 에너지가 발생하는가 ?

– 조깅으로 얼마만큼의 에너지가 소모되나 ?

Dimensional AnalysisHow many eggs in a dozen? 1 dozen = 12

dozen 1

12 eggsdozen 14 168 eggs

For Spring Break going to Palm Beach, FL (1530km)

How long will take if you travel 65miles/hr? (1mi=1.609km)

1.609km

1mi 1.609km 1mi

65mi

1hr

1.609km

1mi1530km 14.6 hrs

Dimensional Analysis• Atomic Mass Unit (amu)

– 1/12th the mass of a carbon-12 atom

• Dalton (D)– new name for amu

Particle Mass Chargeproton 1.0073amu +1neutron 1.0087amu 0electron 0.00055amu -1

Dimensional Analysis• Isotopes 동위원소

– atoms with same number of protons, but with different number of neutrons

1 proton 0 neutrons 1.00782amu

1 proton 1 neutron 2.01410amuH

H21

11

• Isotopic Mass– mass of an isotope relative to the carbon-12

isotope, the standard

Atomic Mass• 원자 질량

– average mass of the isotopes of an element according to their natural abundance

1.0078amu 99.985%

2.0141amu 0.015%H

H21

11

)(1.0080amu 1.00795amu

amu) 2.0141 (0.015%1.0078amu) (99.985% AM

화학식량• Formula Unit (Chemical Formula)

– covalent compounds, C6H12O6

– ionic compounds, NaCl, MgO

• Formula Mass– sum the atomic mass for each atom in the

chemical formula

amu 180.16

16.00 6 1.008 12 12.01 6 )OHFW(C 6126

• Molecular Mass

원자질량단위와 몰

6.02x1023 = 1 mole

• AMU to Mass– 1 amu is 1/12th of carbon - 12 atom– 6.02x1023 amu = 1 gram

• Mole– unit of measurement – Avogadro’s number = 6.02x1023

Final Dimension• Molar Mass

– mole of any substance has a molar mass (grams) equal to the formula mass

mole

gram 180.16

mole 1

6.02x10

amu 6.02x10

gram 1amu 180.16

23

23

1 mole C6H12O6 = 180.16 grams

FW of C6H12O6 = 180.16 amu

Significant Figures• Nonzero digits are significant

• Zeros between nonzero digits are significant

• Zeros to right of the decimal point are significant

• Zeros to left of the decimal point can be ambiguous

• Zeros that precede the first nonzero digit are not significant

Recycling

• Garbage, What is it?– Anything that is no longer wanted or useful

• Why do we recycle?

• What can we recycle?

• How can we recycle?

Waste

• Dispose of 210 million tons of waste

• Cost of 45 billion dollars per year

• 12 billion tons per year– commercial, industrial and municipal

Garbage• Household Garbage

– 42% paper and textiles– 23% metal, plastic and glass– 18% yard waste– 7% food waste

• Landfills– leaching pollutes local water tables– generate methane gas from degraded materials

Fresh Kills Landfill

Paper Recycling• Paper most common recycled material

– between 45-50% of paper is recycled

• Two types of recycled paper– post-commercial paper– post-consumer paper

• Saves 17 trees per ton of paper– 42.3 million tons of paper recycled - 1996

Newspaper Recycling• 1998 - 8.8 million tons of newspaper

– 20% of all paper recycled in the US

• Uses of recycled newspaper– 50% is exported– 17% for paperboard– 18% for miscellaneous paper and non paper

products

• Paper can be recycled three to seven times

Composting• Yard Waste

– grass clipping, leaves, weeds and kitchen waste

• Composting speeds up decay– bacteria, fungi, and microorganisms decompose

the organic material releasing nutrients

• Compost is rich in nutrients for growing

Food Recycling• Food Waste

– makes up most of the smell of garbage– food source for bacteria and parasites

• Clean Food– can be recycled into biogas (methane gas)– burned to heat homes or to produce electricity

• Example: Los Angeles Airport– 16,000 tons of food residual per year

Recycling Plastics• Plastics

– synthetic polymers– long chains of repeating units– plastics are from petroleum products– polyethylene terphthalate (PET), HDPE

• Recycled for non-food applications– 그러나 제조막 사이에 사용되기도 한다

• Recycling plastic is extremely important because they are non-biodegradable

Recycling Plastics• Three methods for recycling plastics

– mechanical recycling

– feedstock recycling

– energy recovery

Waste Water• What happens to the water that you used to

shower, brush your teeth, flush the toilet?

• Sewage - household waste water– water goes to water treatment plant

• Two types of water– gray water - sinks, showers– black water - toilets

Water Recycling• Treatment plant deal with two issues

– solid waste from the water– purifying the water for return to nature

• 7 million tons of dry sludge - 2000– 50-60% use as land fertilizer

• Water purification is expense– filtration, osmosis, dialysis