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CHM 141H Lecture Notes - Lecture 9: Chemical Equation, Molecular Mass, Photosynthesis

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13 Jan 2019

School

Miami University

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Chemistry & Biochemistry

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Document Summary

Balance an element that appears in only one reactant and one product: 2. Balance other elements that appears in only one reactant and one product. If there are no such elements, balance elements that appear in more than one reactant or product. Usually, the element that appears in most reactants and products is balanced last: 3. If one of stoichiometric coefficients is a fraction and you are told to use only integer coefficients multiply all coefficients by the smallest possible integer that will eliminate the fraction. Combustion reactions: combustion reactions are heat-producing reactions between oxygen (o2) and another element or compound, combustion of hydrocarbons (molecules composed of carbon and hydrogen) produce co2 and h2o. Stoichiometric calculations: calculating the mass of a product from the mass of a reactant requires, the mole ratio from the balanced chemical equation, molar mass of the reactant, molar mass of the product. Percent composition: mass percent: mass of element in compound/mass of compound x100.

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Related Questions

I need just the answers for part A&C.. not hand writing!!

Science Tutor: Chemistry Name: Mixtures, Solutions, &Compounds: Chemical Equations Date Chemical Equations If a chemical symbol can be thought of as a letter and a chemical formula as a word in the language of chemistry, then a chemical equation is a statement or sentence. A chemical equation is a shorthand way of describing a chemical reaction between two or more substances. A "+ sign means "combines with." An arrow points away from the reactants and toward the products (See page 10), and an arrow means "yields." 2Na + Cl2 â 2NaCl means sodium combines with chlorine to yield sodiumn chloride (salt) Look closely at the equation above. Notice the "2" in front of NaCI on the right and Na on the left. That 2, called a coefficient, is necessary to make this equation balance. Remember Antoine Lavoisier? (Page 15) Matter is neither created nor destroyed in a chemical reaction. The same number of each kind of atom must be on both sides of a chemical equation. Because chlorine only exists as a molecule consisting of two chlorine atoms, it requires two atoms of sodium to yield two molecules of salt (NaCI). This illustrates another important law stated clearly by the French chemist Joseph-Louis Proust in 1799. Chemical compounds always combine in certain specific fixed proportions. Wherever sodium and chlorine combine, two atoms of sodium will be necessary to react with one molecule of gaseous chlorine. 1 . For the equation 2Mg + O2â 2MgO + energy: A. List the reactant or reactants 2Hato B. List the product or products C. How many atoms of magnesium does it take to combine with one molecule of oxygen? D. How many molecules of magnesium oxide are produced in this reaction? 2. Hydrogen can combine with oxygen to produce water. We could write the equation like this: H2 + O2 â H2O. But this equation is unbalanced! Rewrite this equation with the correct coefficients so that an atom of oxygen doesn't disappear! (Be careful. If you add a coefficient to one side you may have to adjust the other. Count all the atoms.) 3. Now that you have the idea, balance the following equations: A, Pho, â PbO + 02 C. Ca + H2O â Ca(OH)2 + H2 How is following a recipe to mix up a batch of biscuits (or any other food item) similar to Proust's law for chemical reactions? 4. OMark Twain Media, Inc., Publishers 17