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chem lab exp. 6 - Laboratory 6 Chemical Reactions and...

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Laboratory 6 Chemical Reactions and Balancing Chemical Equations Name: Norkhairin Yusuf Partner: Azizah Ahmad Section Section 40, Monday 2 PM Performed: 13 October, 2008 Submitted 13 October, 2008 Laboratory Instructor: Hongmei Yuan Your Signature ___________________________________
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Purpose The purpose of this lab was to observe chemical reactions and balancing chemical equations from two substances mixed. Observed change includes bubbles (evolution of a gas), formation of a solid (precipitation), dissolving of a solid, change of color, production of heat or flame, etc. This shows the chemical changes or reactions. Introduction Observing that a reaction appears to occur (or that it is predicted to occur), a chemical equation is the best way to represent this. For reactions of two compounds, the general “best guess” for the reaction is called metathesis or double replacement . This is where the two positive ions change places (or the two negative ions change places) to form two possible compounds. AB + CD CB + AD It is imperative that the correct formulas are known for all compounds in the proposed equation; otherwise the equation is hopelessly flawed and is not useful to us or to the reader. This means that the common charges on ionic species must be reviewed constantly. Let us use an example where aqueous hydrochloric acid is added to solid calcium carbonate. The observer sees the solid dissolve to form a colorless solution and bubbles are evolved while the dissolving occurs. To begin, let us find the correct formulas for the reactants. Aqueous hydrochloric acid is a strong electrolyte and will be written ionically (H + Cl - ) later; calcium carbonate is a solid and is not ionized, CaCO 3 . Now compare to the general example AB + CD CB + AD Experimental 1) 7 small test tubes are obtained and rinsed with distilled water. By using the dispensing repipet on the reagent bottle, 1ml of each following solutions are added to the respective tubes and color and other observations are recorded in the table on the Data section.
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