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Mass Lab

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The objective of the lab was to understand the Law of Conservation of Mass. The Law of Conservation of Mass states that matter can be changed from one form into another, mixtures can be separated or made, and pure substances can be decomposed, but the total amount of mass remains constant. For example, from our experiment in the lab, we observed mass of the mixture of aqueous Sodium Sulfide and aqueous Zinc chloride turned white color. After the filtration, and all the water was evaporated, we measured the mass very close to what we had started at the beginning. The error in mass occurred because of the remained residue (solute) in the beaker. We were unable to completely clean water, and some mass was added because we couldn’t evaporate …show more content…

(NH4)2Cr2O7(s) → Cr2O3(s) + N2(g) + 4H2O(g) …show more content…

A net ionic equation shows only the species that actually take part in the reaction. In solution, Na2S dissociates into Na and S2 ions and ZnCl2 dissociates into Zn2 and Cl ions. As per our lab, zinc ions (Zn 2) and sulfide ions (S2) formed an insoluble compound, zinc sulfide (ZnS), while the other product, NaCl, was soluble and remains in solution. This reaction is called a precipitation reaction. The balanced molecular equation is: Na2S(aq) + ZnCl2(aq) = ZnS(s) +2NaCl(aq). The ionic and net ionic equations are: Ionic: 2Na(aq) + S2(aq) + Zn2(aq) + 2Cl(aq) ZnS(s) +2Na(aq) + 2Cl(aq), and net ionic: Zn2(aq) + S2 (aq)+ ZnS(s). Chemical reaction occurred from the ammonium dichromate(Decomposition) was exothermic reactions. In a double displacement reaction two compounds exchange bonds or ions in order to form different compounds. An example of a double displacement reaction occurred between zinc chloride and sodium sulfide to form zinc sulfide and sodium chloride. ZnCl2(aq) + Na2S(aq)= ZnS(s) + NaCl(aq). Ionic reactions occurred between ions in aqueous solution. A reaction occurs when a pair of ions come together to produce at least one of the following: a precipitate, a gas, water, or some other non‐ionized substance. An examples of ionic reactions, if a compound is soluble in water then it should be shown as being in aqueous solution, or left as separate ions. Net ionic equations show

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