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Questions in chemistry

[Terjawab] A scientist wants to determine how many moles of bromine $(Br_2)$ are needed to make 8.33 mol of lithium bromide (LiBr). $2 Li+Br_2 \rightarrow 2 LiBr$ How many moles of bromine are needed?

[Terjawab] Magnesium and chlorine react to form an ionic compound. What is the correct name of the compound formed? A. magnesium chloride B. magnesium chlorine C. magnesium chlorite D. magnesium chlorate

[Terjawab] Test your understanding of isotopes by selecting the correct relationship between the pair of atoms ${ }_5^{11} B$ Boron-10 A. Different Element B. Same Atom, Not Isotopes of Each Other C. Isotopes

[Terjawab] The equation for the pH of a substance is [tex]$pH =-\log \left[ H ^{+}\right]$[/tex], where [tex]$H +$[/tex] is the concentration of hydrogen ions. What is the approximate pH of a solution whose hydrogen ion concentration is [tex]$2 \times 10^{-9}$[/tex]?

[Terjawab] A student requires 2.00 L of [tex]$0.100 M NH _4 NO _3$[/tex] from a [tex]$1.75 M NH _4 NO _3$[/tex] stock solution. What is the correct way to get the solution? Use [tex]$M_i V_f=M_f V_f$[/tex]. A. Measure 114 mL of the 1.75 M solution, and dilute it to 1.00 L. B. Measure 114 mL of the 1.75 M solution, and dilute it to 2.00 L. C. Measure 8.75 mL of the 1.75 M solution, and dilute it to 2.00 L. D. Measure 8.75 mL of the 0.100 M solution, and dilute it to 2.00 L.

[Terjawab] A scientist wants to determine how many moles of sodium nitride $(Na_3N)$ could be made from 7.83 mol of nitrogen $(N_2)$. $6 Na+N_2 \rightarrow 2 Na_3 N$ How many moles of sodium nitride could be made?

[Terjawab] Match each group to the correct property. Refer to the periodic table if you need help. alkali metals halogens noble gases solids at room temperature

[Terjawab] Rank these chemical species by increasing pH of an 0.1 M aqueous solution of each. That is, imagine making an 0.1 M solution of each species. Select 1 next to the species that makes the solution with the lowest pH. Select 2 next to the species that makes the solution with the next higher pH, and so on. Notice that some of the rankings have been filled in for you already. Also notice that water is on the list. For that particular case, just compare the pH of pure water to the pH of the other solutions. Note for advanced students: for all charged species, you may assume the necessary counterions act as neither acids nor bases. | species | relative pH of 0.1 M aqueous solution | | :-------------- | :-------------------------------------- | | [tex]$H _3 O ^{+}$[/tex] | 1 (lowest) | | [tex]$C _6 H _5 COOH$[/tex] | -3 | | [tex]$C _6 H _5 COO ^{-}$[/tex] | (Choose one) | | [tex]$HONH _2$[/tex] | 8 (highest) | | [tex]$HONH _3{ }^{+}$[/tex] | (Choose one) | | HCOOH | 2 | | [tex]$HCOO ^{-}$[/tex] | (Choose one) | | [tex]$H _2 O$[/tex] | (Choose one) |

[Terjawab] Which statement best describes a true solution? A. A true solution will settle out after a short period of time. B. A true solution coagulates when heated or boiled. C. A true solution will not separate in a centrifuge. D. A true solution has a cloudy appearance.

[Terjawab] What is the term for the decomposition of a material brought about by heat in the absence of oxygen? A. Pyrolysis B. Conflagration C. Combustion D. Oxidation