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Questions in chemistry

[Terjawab] Consider the following intermediate chemical equations: [tex] \begin{array}{ll} C(s)+O_2(g) \rightarrow CO_2(g) & \Delta H_1=-393.5 kJ \\ 2 CO(g)+O_2(g) \rightarrow 2 CO_2(g) & \Delta H_2=-566.0 kJ \\ 2 H_2 O(g) \rightarrow 2 H_2(g)+O_2(g) & \Delta H_3=483.6 kJ \end{array} [/tex] The overall chemical equation is [tex]$C ( s )+ H _2 O ( g ) \rightarrow CO ( g )+ H _2(g)$[/tex]. To calculate the final enthalpy of the overall chemical equation, which step must occur? A. Reverse the first equation, and change the sign of the enthalpy. Then, add. B. Reverse the second equation, and change the sign of the enthalpy. Then, add. C. Multiply the first equation by three, and triple the enthalpy. Then, add. D. Divide the third equation by two, and double the enthalpy. Then, add.

[Terjawab] Refer to the pH scale in your textbook and answer the following questions. Does a pH of seven indicate more hydrogen ions than hydroxyl ions? If so, why? If not, on a pH of three?

[Terjawab] A scientist wants to determine how many moles of chlorine ([tex]Cl_2[/tex]) are needed to make 116 g of lithium chloride (LiCl). [tex]2 Li+Cl_2 \rightarrow 2 LiCl[/tex] The molar mass of each substance is provided in the table below. | Substance | Molar Mass (g/mol) | | :-------- | :----------------- | | Lithium (Li) | 6.97 | | Chlorine ([tex]Cl_2[/tex]) | 70.90 | | Lithium chloride (LiCl) | 42.42 | How many moles of chlorine are needed?

[Terjawab] Since 1995, supplies of CFC refrigerants used to service existing refrigeration appliances in the United States can only come from A. third-world chemical companies B. European manufacturers C. recovery and recycling D. solvent conversion

[Terjawab] What happens when the electron moves from the first energy level to the second energy level?

[Terjawab] 3.2 The redox reaction below is used to construct an electrochemical cell. [tex]Fe^{2+}(aq) + Ag^{+}(aq) \rightarrow Ag(s) + Fe^{3+}(aq)[/tex] 3.2.1 Define oxidation in terms of oxidation number. 3.2.2 Name a substance that should be used as electrode in the anode half-cell. 3.2.3 Write down the NAME or FORMULA of the oxidizing agent. 3.2.4 Write down the cell notation of the cell.

[Terjawab] Select the correct answer. What is the formula of the compound vanadium(V) oxide? Use the list of polyatomic ions and the periodic table to help you answer. A. $VO _2$ B. $VO _5$ C. $V _5 O _2$ D. $V _2 O _5$ E. $V _2 O _2$

[Terjawab] Consider the following intermediate chemical equations. [tex] \begin{array}{l} C(s)+\frac{1}{2} O_2(g) \rightarrow CO(g) \\ CO(g)+\frac{1}{2} O_2(g) \rightarrow CO_2(g) \end{array} [/tex] When you form the final chemical equation, what should you do with CO? A. Cancel out CO because it appears as a reactant in one intermediate reaction and a product in the other intermediate reaction. B. Add the two CO molecules together, and write them as reactants in the final chemical reaction. C. Write CO only once as a reactant in the final chemical reaction. D. Write CO as a reactant and a product in the final chemical reaction.

[Terjawab] 2,2-dimethyl-1-pentanol, 2-methyl-2-pentanol and 2-methyl-3-pentanol are: A. Primary alcohol, secondary alcohol and tertiary alcohol, respectively B. Secondary alcohol, primary alcohol and tertiary alcohol, respectively C. Tertiary alcohol, secondary alcohol and primary alcohol, respectively D. Primary alcohol, tertiary alcohol and secondary alcohol, respectively

[Terjawab] An electric device delivers a current of [tex]$15.0 A$[/tex] for 30 seconds. How many electrons flow through it?