Chapter 4 Chemical Reaction & Recycling 재활용과 화학수학

Topics Balanced Chemical Equations Stoichiometry Formula Mass Avogadro’s Number, 6.02x10 23 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 –C 6 H 12 O 6 + O 2  CO 2 + H 2 O + Energy 글루코오스이산화탄소 + 물 –a C 6 H 12 O 6 + b O 2  c CO 2 + d H 2 O 반응물  생성물

Chemical Reactions Respiration –C 6 H 12 O 6 + O 2  CO 2 + H 2 O + Energy –a C 6 H 12 O 6 + b O 2  c CO 2 + d H 2 O –1 C 6 H 12 O O 2  6 CO H 2 O

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) – H 2 + N 2  NH 3 – 3 H 2 + N 2  2 NH 3 Changes in reaction conditions affect outcome of a reaction Commercial reaction are optimized for products and cost

Chemical Reactions Ozone to Oxygen – 2 O 3  3 O 2 – 중간 화학종 intermediate species O 3  O 2 + O O + O 3  2 O 2 O + 2 O 3  3 O 2 + 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 Al 2 O 3 + C  Al + CO 2 2 Al 2 O C  4 Al + 3 CO 2

Stoichiometry 화학양론 – 화학과정에서 사용되거나 생성된 물질의 상대적 양을 결정하는 학문 –2 Al 2 O C  4 Al + 3 CO 2 Answers Questions – 알루미늄 깡통 한 개를 만들기 위해서 얼마만큼의 Al 2 O 3 과 에너지가 필요한가 ? – 천연 가스 1 몰이 타면 얼마만큼의 에너지가 발생하는가 ? – 조깅으로 얼마만큼의 에너지가 소모되나 ?

Dimensional Analysis How many eggs in a dozen? 1 dozen = eggs For Spring Break going to Palm Beach, FL (1530km) How long will take if you travel 65miles/hr? (1mi=1.609km) 14.6 hrs

Dimensional Analysis Atomic Mass Unit (amu) –1/12th the mass of a carbon-12 atom Dalton (D) –new name for amu

Dimensional Analysis Isotopes 동위원소 –atoms with same number of protons, but with different number of neutrons 1 proton0 neutrons amu 1 proton1 neutron amu 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 amu99.985% amu0.015%

화학식량 Formula Unit (Chemical Formula) –covalent compounds, C 6 H 12 O 6 –ionic compounds, NaCl, MgO Formula Mass –sum the atomic mass for each atom in the chemical formula Molecular Mass

원자질량단위와 몰 6.02x10 23 = 1 mole AMU to Mass –1 amu is 1/12th of carbon - 12 atom –6.02x10 23 amu = 1 gram Mole –unit of measurement –Avogadro’s number = 6.02x10 23

Final Dimension Molar Mass –mole of any substance has a molar mass (grams) equal to the formula mass 1 mole C 6 H 12 O 6 = grams FW of C 6 H 12 O 6 = 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

Newspaper Recycling 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 –50-60% use as land fertilizer Water purification is expense –filtration, osmosis, dialysis