Formal Charge Example Problem

Formal Charge Example Problem Resonance structures are all the possible Lewis structures for a molecule. Formal charge is a technique to identify which resonance structure is the more correct structure. The most correct Lewis structure will be the structure where the formal charges are evenly distributed throughout the molecule. The sum of all the formal charges should equal the total charge of the molecule.Formal charge is the difference between the number of valence electrons of each atom and the number of electrons the atom is associated with. The equation takes the form:FC eV - eN - eB/2whereeV number of valence electrons of the atom as if it were isolated from the moleculeeN number of unbound valence electrons on the atom in the moleculeeB number of electrons shared by the bonds to other atoms in the moleculeThe two resonance structures in the above picture are for carbon dioxide, CO2. To determine which diagram is the correct one, the formal charges for each atom must be calculated.For Structure A:eV fo r oxygen 6eV for carbon 4To find eN, count the number of electron dots around the atom. eN for O1 4eN for C 0eN for O2 4To find eB, count the bonds to the atom. Each bond is formed by two electrons, one donated from each atom involved in the bond. Multiply each bond by two to get the total number of electrons.eB for O1 2 bonds 4 electronseB for C 4 bonds 8 electronseB for O2 2 bonds 4 electronsUse these three values to calculate the formal charge on each atom. Formal charge of O1 eV - eN - eB/2Formal charge of O1 6 - 4 - 4/2Formal charge of O1 6 - 4 - 2Formal charge of O1 0Formal charge of C eV - eN - eB/2Formal charge of C1 4 - 0 - 4/2Formal charge of O1 4 - 0 - 2Formal charge of O1 0Formal charge of O2 eV - eN - eB/2Formal charge of O2 6 - 4 - 4/2Formal charge of O2 6 - 4 - 2Formal charge of O2 0For Structure B:eN for O1 2eN for C 0eN for O2 6Formal charge of O1 eV - eN - eB/2Formal charge of O1 6 - 2 - 6/2Formal charge of O1 6 - 2 - 3Formal charge of O1 1Formal charge of C eV - eN - eB/2Formal charge of C1 4 - 0 - 4/2Formal charge of O1 4 - 0 - 2Formal charge of O1 0Formal charge of O2 eV - eN - eB/2Formal charge of O2 6 - 6 - 2/2Formal charge of O2 6 - 6 - 1Formal charge of O2 -1All the formal charges on Structure A equal zero, where the formal charges on Structure B show one end is positively charged and the other is negatively charged. Since the overall distribution of Structure A is zero, Structure A is th e most correct Lewis structure for CO2.

Effects of Carbon Monoxide on the Body

Effects of Carbon Monoxide on the Body Carbon Monoxide (CO) Carbon monoxide is a colorless, odorless, tasteless and toxic gas produced as a bys of carbon monoxide producing devices commonly in use around the home include: Fuel fired furnaces (non-electric)Gas water heatersFireplaces and woodstovesGas stovesGas dryersCharcoal grillsLawnmowers, snowblowers and other yard equipmentAutomobiles Medical Effects of Carbon Monoxide Carbon monoxide inhibits the bloods ability to carry oxygen to body tissues including vital organs such as the heart and brain. When CO is inhaled, it combines with the oxygen carrying hemoglobin of the blood to form carboxyhemoglobin (COHb). Once combined with the hemoglobin, that hemoglobin is no longer available for transporting oxygen. How quickly the carboxyhemoglobin builds up is a factor of the concentration of the gas being inhaled (measured in parts per million or PPM) and the duration of the exposure. Compounding the effects of the exposure is the long half-life of carboxyhemoglobin in the blood. Half-life is a measure of how quickly levels return to normal. The half-life of carboxyhemoglobin is approximately 5 hours. This means that for a given exposure level, it will take about 5 hours for the level of carboxyhemoglobin in the blood to drop to half its current level after the exposure is terminated. Symptoms Associated With a Given Concentration of COHb 10% COHb - No symptoms. Heavy smokers can have as much as 9% COHb. 15% COHb - Mild headache. 25% COHb - Nausea and serious headache. Fairly quick recovery after treatment with oxygen and/or fresh air. 30% COHb - Symptoms intensify. Potential for long term effects especially in the case of infants, children, the elderly, victims of heart disease and pregnant women. 45% COHb - Unconsciousness 50% COHb - Death Since one cant easily measure COHb levels outside of a medical environment, CO toxicity levels are usually expressed in airborne concentration levels (PPM) and duration of exposure. Expressed in this way, symptoms of exposure can be stated as in the Symptoms Associated With a Given Concentration of CO Over Time table below. As can be seen from the table, the symptoms vary widely based on exposure level, duration and the general health and age on an individual. Also note the one recurrent theme that is most significant in the recognition of carbon monoxide poisoning - headache, dizziness and nausea. These flu like symptoms are often mistaken for a real case of the flu and can result in delayed or misdiagnosed treatment. When experienced in conjunction with the sounding of a carbon monoxide detector, these symptoms are the best indicator that a potentially serious buildup of carbon monoxide exists. Symptoms Associated With a Given Concentration of CO Over Time PPM CO Time Symptoms 35 8 hours Maximum exposure allowed by OSHA in the workplace over an eight hour period. 200 2-3 hours Mild headache, fatigue, nausea and dizziness. 400 1-2 hours Serious headache-other symptoms intensify. Life threatening after 3 hours. 800 45 minutes Dizziness, nausea and convulsions. Unconscious within 2 hours. Death within 2-3 hours. 1600 20 minutes Headache, dizziness and nausea. Death within 1 hour. 3200 5-10 minutes Headache, dizziness and nausea. Death within 1 hour. 6400 1-2 minutes Headache, dizziness and nausea. Death within 25-30 minutes. 12,800 1-3 minutes Death Source: Copyright 1995, H. Brandon Guest and Hamel Volunteer Fire DepartmentRights to reproduce granted provided copyright information and this statement included in their entirety. This document provided for informational purposes only. No warranty with respect to suitability for use expressed or implied.