Regents Chemistry Test Preparation Practice

    Moles And Stoichiometry

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    Base your answers to questions 9 on the information below and on your knowledge of chemistry.

    During a laboratory activity, appropriate safety equipment was used and safety procedures were followed. A laboratory technician heated a sample of solid KClO3 in a crucible to determine the percent composition by mass of oxygen in the compound. The unbalanced equation and the data for the decomposition of solid KClO3 are shown below.

    compounds fig: chem62019-exam_g14.png

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    Base your answers to questions 10 on the information below and on your knowledge of chemistry.

    Thermal energy is absorbed as chemical reactions occur during the process of baking muffins. The batter for muffins often contains baking soda, NaHCO3(s), which decomposes as the muffins are baked in an oven at 200.°C. The balanced equation below represents this reaction, which releases CO2(g) and causes the muffins to rise as they bake. The H2O(ℓ) is released into the air of the oven as it becomes a vapor.

    2NaHCO3(s) + heat → Na2CO3(s) + H2O(ℓ) + CO2(g)

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    Base your answers to questions 11 on the information below and on your knowledge of chemistry.

    A sample of seawater is analyzed. The table below gives the concentration of some ions in the sample.

    compounds fig: chem62015-exam_g15.png

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    Base your answers to questions 12 on the information below and on your knowledge of chemistry.

    Baking soda, NaHCO3, can be commercially produced during a series of chemical reactions called the Solvay process. In this process, NH3(aq), NaCl(aq), and other chemicals are used to produce NaHCO3(s) and NH4Cl(aq).

    To reduce production costs, NH3(aq) is recovered from NH4Cl(aq) through a different series of reactions. This series of reactions can be summarized by the overall reaction represented by the unbalanced equation below.

    NH4Cl(aq) + CaO(s) → NH3(aq) + H2O(ℓ) + CaCl2(aq)

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    Base your answers to questions 13 on the information below and on your knowledge of chemistry.

    One process used to manufacture sulfuric acid is called the contact process. One step in this process, the reaction between sulfur dioxide and oxygen, is represented by the forward reaction in the system at equilibrium shown below.

    2SO2(g) + O2(g) ⇌ 2SO3(g) + 394 kJ

    A mixture of platinum and vanadium(V) oxide may be used as a catalyst for this reaction. The sulfur trioxide produced is then used to make sulfuric acid.

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    Base your answers to questions 14 on the information below and on your knowledge of chemistry.

    In the late 19th century, the Hall-Herroult process was invented as an inexpensive way to produce aluminum. In this process, Al2O3(ℓ) extracted from bauxite is dissolved in Na3AlF6(ℓ) in a graphite-lined tank, as shown in the diagram below. The products are carbon dioxide and molten aluminum metal.

    classification-of-matter fig: chem62013-exam_g18.png

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    Base your answers to questions 15 on the information below.

    Calcium reacts with water. This reaction is represented by the balanced equation below. The aqueous product of this reaction can be heated to evaporate the water, leaving a white solid, Ca(OH)2(s).

    Ca(s) + 2H2O(ℓ) → Ca(OH)2(aq) + H2(g)

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