Chap 7,8,9
How many valence electrons does germanium (Ge) have?
4
Which of the listed elements is most metallic? Which of the listed elements is most metallic? Al Cl H B
Al
What is the electron configuration of arsenic (As)? What is the electron configuration of arsenic ()? [Ar]4s24d104p3 [Ar]4s24p3 [Ar]4s23d64p3 [Ar]4s23d104p3
As is in Group 5A, in the fourth period, and has 33 electrons. The previous noble gas is Ar ([Ar]) at the end of the third period with 18 electrons. Moving across, the fourth period fills the 4s level, then the 3d and the 4p levels. The remaining 15 electrons (33−18) fill these orbitals in order of increasing energy [Ar]4s23d104p3.
Order the elements Ba, Sr, and Te in order of decreasing atomic size. Order the elements , , and in order of decreasing atomic size. Te > Ba > Sr Te > Sr > Ba Ba > Sr > Te Sr > Te > Ba
Ba > Sr > Te
Which statement best describes an endothermic reaction?
By definition, endothermic reactions absorb thermal energy from the surroundings.
Hydrogen gas reacts with oxygen to form water. 2H2(g)+O2(g)→2H2O(g)ΔH=−483.5kJ Determine the minimum mass of hydrogen gas required to produce 229 kJ of heat.
Energy ⟶ molH2 ⟶ gH2 2molH2−483.5kJ 2.02gH21molH2 −229kJ×2molH2−483.5kJ×2.02gH21molH2=1.91gH2
When sodium forms an ion, it loses electrons. How many electrons does it lose, and which orbitals do the electrons come from? When sodium forms an ion, it loses electrons. How many electrons does it lose, and which orbitals do the electrons come from? five electrons from the 3p orbital three electrons: two from the 3s orbital and one from the 3p orbital one electron from the 3s orbital three electrons: one from the 3s orbital and two from the 2s orbital
Na forms a predictable charge based on its number of valence electrons. Its predictable charge is based on the atom attaining a noble gas electron configuration (with filled outermost s and p orbitals). Na:1s22s22p63s1 Losing one electron from the 3s orbital, results in the same configuration as Ne. 1s22s22p6 The loss of three electrons results in a cation with a charge of 1+.
Which of the listed elements has the highest ionization energy? Which of the listed elements has the highest ionization energy? Ne Ca S As
Ne
The element sulfur forms an ion with what charge?
Sulfur forms a predictable charge based on its number of valence electrons. The sulfur ion's predictable charge is based on the atom attaining a noble gas electron configuration (with filled outermost s and p orbitals). S:1s22s22p63s23p4 Gaining two electrons in the 3p orbital produces the same configuration as Ar. 1s22s22p63s23p6 Gaining two electrons produces an anion with a charge of 2−.
Sodium and chlorine react to form sodium chloride. 2Na(s)+Cl2(g)→2NaCl(s) What is the theoretical yield of sodium chloride for the reaction of 57.9 gNa with 70.7 gCl2?
The theoretical yield is the amount of product produced by the limiting reactant. gNa ⟶ molNa ⟶ molNaCl ⟶ gNaCl 1molNa22.99gNa 2molNaCl2molNa 58.44gNaCl1molNaCl 57.9gNa×1molNa22.99gNa×2molNaCl2molNa×58.44gNaCl1molNaCl=147gNaCl=1.47×102gNaCl gCl2 ⟶ molCl2 ⟶ molNaCl ⟶ gNaCl 1molCl270.90gCl2 2molNaCl1molCl2 58.44gNaCl1molNaCl 70.7gCl2×1molCl270.90gCl2×2molNaCl1molCl2×58.44gNaCl1molNaCl=117gNaCl
Which set of wavelengths for light are arranged in order of increasing frequency? 300 nm; 250 nm; 350 nm 350 nm; 300 nm; 250 nm 250 nm; 300 nm; 350 nm 300 nm; 350 nm; 250 nm
Wavelength and frequency are inversely proportional: as wavelength decreases , the frequency increases 350 nm;300nm;250nm
Titanium can be obtained from its oxide by the reaction shown here. When 42.0 g of TiO2 react with 11.5 gC, 16.0 gTi are obtained. What is the percent yield for the reaction? TiO2(s)+2C(s)→Ti(s)+2CO(g)
gTiO2 ⟶ molTiO2 ⟶ molTi ⟶ gTi 1molTiO279.88gTiO2 1molTi1molTiO2 47.88gTi1molTi 42.0gTiO2×1molTiO279.88gTiO2×1molTi1molTiO2×47.88gTi1molTi=25.2gTi gC ⟶ molC ⟶ molTi ⟶ gTi 1molC12.01gC 1molTi2molC 47.88gTi1molTi 11.5gC×1molC12.01gC×1molTi2molC×47.88gTi1molTi=22.9gTi percentyield=actualyieldtheoreticalyield×100%=16.0g22.9g×100%=69.8%
Which property decreases as you move down a column in the periodic table? Which property decreases as you move down a column in the periodic table? atomic size ionization energy metallic character none of the above (all decrease as you move down a column).
ionization energy
Consider the generic reaction: A+2B→AB2ΔHrxn=−155kJ If a reaction mixture contains 5 molA and 6 molB, how much heat is emitted or absorbed once the reaction has occurred to the greatest extent possible?
molA ⟶ Energy −155kJ1molA 5molA×−155kJ1molA=−775kJ molB ⟶ Energy −155kJ2molB 6molB×−155kJ2molB=−465kJ
Consider the hypothetical reaction shown here. If 13 mol of A combine with 19 mol of B and the reaction occurs to the greatest extent possible, how many mol of C form? 3A+4B→2C
molA ⟶ molC 2molC3molA 13molA×2molC3molA=8.7molC molB ⟶ molC 2molC4molB 19molB×2molC4molB=9.5molC
Consider the generic reaction: 2A+3B+C→2D A reaction mixture contains 7 molA; 8 molB and 6 molC. What is the limiting reactant?
molA ⟶ molD 2molD2molA 7molA×2molD2molA=7molD molB ⟶ molD 2molD3molB 8molB×2molD3molB=5molD (rounded from 5.33) molC ⟶ molD 2molD1molC 6molC×2molD1molC=12molD
Methanol (CH3OH) reacts with oxygen to form carbon dioxide and water according to the reaction shown here. 2CH3OH(g)+3O2(g)→2CO2(g)+4H2O(g)
moleculesO2 ⟶ moleculesCO2 2moleculesCO23moleculesO2 3moleculesO2×2moleculesCO23moleculesO2=2moleculesCO2 moleculesCH3OH ⟶ moleculesCO2 2moleculesCO22moleculesCH3OH 3moleculesCH3OH×2moleculesCO22moleculesCH3OH=3moleculesCO2 O2 is limiting so no O2 is left in the reaction mixture. Two molecules of CO2 are present in the reaction mixture. Similar calculations show that 4 molecules of H2O form and that 2 molecules of CH3OH are consumed leaving 1 molecule of CH3OH in the reaction mixture.
A reaction has a theoretical yield of 26.1 g. When the reaction is carried out, 12.9 g of the product is obtained. What is the percent yield?
percentyield=actualyieldtheoreticalyield×100%=12.9g26.1g×100%=49.4%
