Redox Reactions
What is Nitrogen's oxidation number in NO2-. Show you work.
+3
C₂H₆ + O₂ → CO₂ + H₂O (balanced first!)
If 2 moles of C₂H₆ react, how many moles of CO₂ form?
(Balanced: 2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O)
Answer → 4 moles CO₂
A rigid container holds a gas at 150 kPa and 27°C. What is the pressure of the gas at 127°C?
27°C = 300 K
127°C = 400 K
P₂ = 200 kPa
A region was contaminated with 640 g of Cs-137 in 1986. How much Cs-137 will remain in 2076? Show each half-life step clearly.
80
Which electron configuration represents the electrons in neon in an excited state.
2-7-1
Predict whether this reaction occurs and why there is a difference:
Cu + AgNO₃ → Cu(NO₃)₂ + Ag
and
Ag + CuSO₄ → Ag₂SO₄ + Cu
spontaneous / yes
Copper is above silver on Table J, so Cu can transfer electrons to Ag⁺.
nonspontaneous / no reaction
Silver is below copper on Table J, so silver does not give electrons to copper ions.
A 15.0 g sample of BaCl₂•xH₂O is heated and loses 2.70 g of water.
Find the percent composition of water in the hydrate.
18% water
A 100.0‑gram sample of H₂O at 22.0∘C22.0∘C absorbs 8360 J8360 J. Using c=4.18 J/g⋅Kc=4.18 J/g⋅K, find the final temperature. Show all steps and justify whether any phase changes occur.
Use q=mcΔTq=mcΔT: ΔT=qmc=8360(100.0)(4.18)≈20.0∘CΔT=mcq=(100.0)(4.18)8360≈20.0∘C so final ≈42.0∘C≈42.0∘C (check phase: no phase change because final <100°C)
What is the penetrating power of the particles from most to least power.
Gamma, beta, alpha
In a sealed rigid cylinder with a movable piston, a sample of H2 gas occupies 30.0 L at 50.0 kPa and 200 K. What is the pressure of the gas if the volume is changed to 60.0 L and the gas is heated to 300 K?
37.5 kPa
Why do eelctrons flow from Zn to Cu in a voltaic cell using table J.
Zn is more reaction and it is higher on Table J. This means it is the anode which means it is being oxidized and loses electrons.
How many moles are in 120 g of MgSO₄?
1 mole
A 250‑gram sample of a substance has a boiling point of 120∘C and a heat of vaporization of 2.10×103 J/g. If heat is supplied at a constant rate of 1250 J/min, calculate the time (in minutes and seconds) required to completely vaporize the sample once it reaches the boiling point. Show the formula and all steps.
Time=420min
What is a fission reaction and what are the risks and benefits of it.
Fission reaction is when a neutron strikes the core of a strong heavy nuclei and it splits into smaller nuclei. A benefit is nuclear power plants do not release greenhouse gasses. Negative of highly reactive waste that is difficult to get rid of.
What is the number of electrons shared between the carbon atoms in an ethene molecule?
4 electrons
Is en Electroylitc cells spontaneous or spontaneous?
nonspontaneous
A compound has empirical formula NO₂ and molar mass 92 g/mol.
Find the molecular formula.
N₂O₄
Using the terms melting, boiling, freezing, condensation, what phase changes use the heat of vaporization equation and heat of fusion equation? Then, explain what specific phase change is occurring with each of these four terms.
Heat of vaporization: Boiling (l-g)/condensation (g-l).
Heat of fusion: Melting (s-l) /freezing (l-s).
Explain why long-lived radioisotopes present a greater long-term storage challenge than short-lived ones. Give an example of a long and short radioisotope decay mode.
Long lived radioisotopes present a greater challenge because they take longer to decay and can negatively impact health unlike short half-lives where the easier to store because they go away faster. Short half life is positron and long half life is alpha decay.
What is the change in oxidation state for aluminum in this reaction:
4Al(2)+ + 3O2(g) arrow 2Al2O3(2)
0 to +3
What side are the electrons put on for an oxidized half reaction and a reduction half reaction and why?
Oxidized is put on the product side and reducation is put on the reactant side. The product side loses electrons which is what oxidization is and the reactant side gains electrons which is what reduction is.
Balance the equation using the smallest whole numbers:
__ Na₃PO₄ + __ CaCl₂ → __ Ca₃(PO₄)₂ + __ NaCl
2Na₃PO₄ + 3CaCl₂ → Ca₃(PO₄)₂ + 6NaCl
Provide a particle‑diagram description (text only) of a sample that is (a) a pure compound, (b) a homogeneous mixture, and (c) a heterogeneous mixture. For each, state what students should look for in a drawn diagram.
(a) pure compound: all particles identical molecules bonded in same arrangement; (b) homogeneous mixture: different molecule types uniformly distributed; (c) heterogeneous: distinct regions or clusters of different components.
Which fraction of an original 20.00 gram sample of nitrogen-16 remains unchanged after 36 seconds.
1/32
Based on table F, identify one positive ion that forms an insoluble compound with iodide ions in an aqueous solution?
Hg2+, Pb2+, Ag+