VincenTragosta - Tanya, Jawab, dan Belajar Tanpa Batas Logo

Questions in chemistry

[Terjawab] Select the correct answer from each drop-down menu. Mendeleev's table of elements was better accepted than those of other scientists at the time because Moseley went a step further in suggesting that the elements be arranged according to

[Terjawab] Select the best answer for the question. 14. On the pH scale, which value is considered neutral? A. 5 B. 7 C. 2 D. 11

[Terjawab] Select the correct answer. The half reaction of an oxidation-reduction reaction shows that iron gains electrons. What does this electron gain mean for iron? A. It is neutralized. B. It is oxidized. C. It is reduced. D. It has dissolved. E. It has precipitated.

[Terjawab] Niobium-91 has a half-life of 680 years. After 2,040 years, how much niobium-91 will remain from a $300.0-g$ sample? A. 3 g B. 18.75 g C. 37.5 g D. 100.0 g

[Terjawab] Now that we have put a coefficient of 2 in front of $NaNO_3$ and a coefficient of 1 in front of $PbCl_2$, what coefficient should go in front of NaCl to balance both the Cl atoms and the Na atoms? $Pb(NO_3)_2+? NaCl \rightarrow 1 PbCl_2+2 NaNO_3$ Express your answer numerically as an integer.

[Terjawab] What is the rate constant of a reaction if rate $=1 \times 10^{-2}(mol / L ) / s ,[ A ]$ is 2 M , [B] is $3 M, m=2$, and $n=1$ ? $k=\frac{\text { rate }}{|A|^r|B|^r}$ A. $8.3 \times 10^{-4}$ B. $1.7 \times 10^5$ C. $2.5 \times 10^{-3}$ D. $60 \times 10^4$

[Terjawab] Use Table B in your Student Guide to answer the questions about ion concentrations. A solution with a [tex]$pH =13$[/tex] has approximately how many moles of [tex]$OH ^{-}$[/tex] ions per liter? How many moles of [tex]$H ^{+}$[/tex] would this same solution have per liter? (Use the decimal form of your answer.) A different solution with an [tex]$H +$[/tex] concentration of [tex]$1.0 \times 10^{-4}$[/tex] would have a [tex]$pH =$[/tex]?

[Terjawab] Present the periodic table.

[Terjawab] A flammable gas that is leaking out of a compressed gas cylinder will burn or possibly explode if it finds... A. an ignition source. B. an open window. C. a nebulizer. D. Both B and C are correct.

[Terjawab] A chemical reaction is represented by the following unbalanced chemical equation: [tex]$Na _2( aq )+ HCl ( aq ) \rightarrow NaCl ( aq )+ H _2 S( g )$[/tex] Which statement best describes why it is necessary to balance all chemical equations? A. Chemical reactions do not destroy matter, so the same number of atoms must be present before and after the reaction. B. Chemical reactions make new substances, so the new elements must be accounted for. C. The total number of atoms in a chemical reaction are relative, so you can add as many as you want. D. The total number of atoms in a chemical reaction can change as the reaction proceeds, so they must be identified first.