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Questions in chemistry

[Terjawab] Which is a characteristic of mixtures? A. They are chemically bonded together. B. They can be classified as pure substances. C. They have fixed ratios between their components. D. They can be separated by physical processes.

[Terjawab] Which is a strong base? HCl NaOH [tex]$NH _3$[/tex] [tex]$H _3 CO _3$[/tex]

[Terjawab] For the isotope ${ }^{71} Ga , Z =$ $\qquad$ and $A =$ $\qquad$ A. 31; 40 B. $31 ; 69.723$ C. 71; 31 D. $71 ; 40$ E. 31; 71

[Terjawab] What information does an energy diagram give? A. It shows the rate of the reaction as a function of time. B. It shows the transfer of potential energy to kinetic energy. C. It shows the energy requirements needed in order for a reaction to occur. D. It shows how concentrations of reactants affect the energy.

[Terjawab] What is the rate of a reaction if the value of [tex]k[/tex] is 0.1, [tex][A][/tex] is 1 M, and [tex][B][/tex] is 2 M? Rate [tex]=k[A]^2[B]^2[/tex] A. [tex]0.8(mol / L ) / s[/tex] B. [tex]0.4(mol / L ) / s[/tex] C. [tex]0.2(mol / L ) / s[/tex] D. [tex]1.6(mol / tL ) / s[/tex]

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

[Terjawab] Select the correct answer. Which element or compound has lost electrons in this oxidation-reduction reaction? [tex]4 Li+2 CoO \rightarrow 2 Co+2 Li_2 O[/tex] A. CoO B. [tex]Li _2 O[/tex] C. Li D. Co E. [tex]O[/tex]

[Terjawab] The table below gives the atomic mass and relative abundance values for the three isotopes of element M. | Relative abundance (%) | Atomic mass (amu) | | :---------------------- | :----------------- | | 78.99 | 23.9850 | | 10.00 | 24.9858 | | 11.01 | 25.9826 | What is the average atomic mass (in amu) of element M?

[Terjawab] Which of the following is the correct Lewis structure for dicarbon tetrahydride, [tex]C_2H_4[/tex], also known as ethene?

[Terjawab] Ethyne ( [tex]$C _2 H _2$[/tex] (g), [tex]$\Delta H_f=226.77 kJ / mol$[/tex] ) undergoes complete combustion in the presence of oxygen to produce carbon dioxide ([tex]$CO _2(g), \Delta H_f=-393.5 kJ / mol$[/tex]) and water ([tex]$H _2 O ( g ), \Delta H_f=-241.82 kJ / mol$[/tex]) according to the equation below. [tex]$2 C_2 H_2(g)+5 O_2(g) \rightarrow 4 CO_2(g)+2 H_2 O(g)$[/tex] What is the enthalpy of combustion (per mole) of [tex]$C _2 H _2(g)$[/tex]? Use [tex]$\Delta H_{r \times n}=\sum\left(\Delta H_{f, \text { products }}\right)-\sum\left(\Delta H_{f, \text { reactants }}\right)$[/tex]. A. -2511.2 kJ / mol B. -1255.6 kJ / mol C. -862.1 kJ / mol D. -431.0 kJ / mol