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Questions in chemistry

[Done] Consider the equation below. [tex]$CaCO_3(s) \longleftrightarrow CaO(s)+CO_2(g)$[/tex] What is the equilibrium constant expression for the given reaction? A. [tex]$K _{ eq }=\frac{[ CaO ]}{\left[ CaCO _3\right]}$[/tex] B. [tex]$K _{\text {eq }}=\frac{\left[ CO _2\right][ CaO ]}{\left[ CaCO _3\right]}$[/tex] C. [tex]$K _{\text {eq }}=\left[ CO _2\right]$[/tex] D. [tex]$K_{\text {eq }}=\frac{1}{\left[ CO _2\right]}$[/tex]

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

[Done] The masses of two samples were measured. What is the total mass, reported to the appropriate number of significant figures? [tex]$24.964 g + 0.7643 g = [?] g$[/tex]

[Done] Sulfuric acid is manufactured industrially by a four-step process as shown: Step 1: Sulfur is burned in excess air to produce sulfur dioxide. Step 2: Sulfur dioxide is converted into sulfur trioxide. Step 3: Sulfur trioxide is reacted with concentrated sulfuric acid to produce Substance Y. Step 4: Substance Y is reacted with water to produce concentrated sulfuric acid. (a) (i) Name the process used in the industrial manufacture of sulfuric acid. (ii) Identify substance Y produced in Step 3. (b) By writing the balanced chemical equation, describe how sulfur dioxide is converted into sulfur trioxide in Step 2.

[Done] How many chlorine atoms are on the products side of the reaction [tex]2 Al +6 HCl \rightarrow 2 AlCl ^2+3 H _2[/tex]?

[Done] A scientist has 100 milligrams of a radioactive element. The amount of radioactive element remaining after [tex]$t$[/tex] days can be determined using the equation [tex]$f(t)=100\left(\frac{1}{2}\right)^{\frac{t}{10}}$[/tex]. After three days, the scientist receives a second shipment of 100 milligrams of the same element. The equation used to represent the amount of shipment 2 remaining after [tex]$t$[/tex] days is [tex]$f(t)=100\left(\frac{1}{2}\right)^{\frac{t-3}{10}}$[/tex]. After any time, [tex]$t$[/tex], the mass of the element remaining in shipment 1 is what percentage of the mass the element remaining in shipment 2? A. 78.1 % B. 81.2 % C. 123.1 % D. 128.0%

[Done] 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.

[Done] 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?

[Done] 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?

[Done] 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