AP Chem MC
Oxygen is oxidized and hydrogen is reduced; oxygen is oxidized and reduced
2H2O2(aq) → 2H2O(l) + O2(g) The decomposition of H2O2(aq) is represented by the equation above. Which of the following identifies the element(s) being oxidized and reduced in the reaction ?
10
2MnO4-(aq) + 10Br-(aq) + 16H+(aq) → 2Mn2+(aq) + 5Br2(aq) + 8H2O(l) How many electrons are transferred in the reaction represented by the balanced equation above?
Oxygen, which changes from -1 to 0
5H2O2(aq) + 2MnO4-(aq) + 6H+(aq) → 2Mn2+(aq) + 8H2O(l) + 5O2(g) In a titration experiment, H2O2(aq) reacts with MnO4-(aq) as represented by the equation above. The dark purple KMnO4 solution is added from a buret to a colorless, acidified solution of H2O2(aq) in an Erlenmeyer flask. (Note: At the end point of the titration, the solution is a pale pink color.) Which element is being oxidized during the titration, and what is the element's change in oxidation number?
CaO
According to the information in the table above, a 1.00 g sample of which of the following contains the greatest mass of oxygen?
C4H8
Complete combustion of a sample of a hydrocarbon in excess oxygen produces equimolar quantities of carbon dioxide and water. Which of the following could be the molecular formula for the compound?
It is a redox reaction, because Cu(s) is oxidized and the nitrogen atom in NO3-(aq) is reduced
Cu(s) + 4HNO3(aq) → Cu(NO3)2(aq) + 2NO2(g) + 2H2O(l) Which of the following is true about the reaction?
0.22 L of H2 has been produced
Fe(s) + 2HCl(aq) → FeCl2(aq) + H2(g) When a student adds 30.0 mL of 1.00 M HCl to 0.56 g of powdered Fe, a reaction occurs according to the equation above. When the reaction is complete at 273 K and 1.0 atm, which of the following is true?
Benzene C6H6
If equal masses of the following compounds undergo complete combustion, which will yield the greatest mass of CO2?
CrO2
In which of the following compounds is the mass ratio of chromium to oxygen closest to 1.62 to 1.00?
KCl and Cl2 only
K(s) + Cl2(g) → KCl(s) ΔH° = -437 kJ/molrxn The elements K and Cl react directly to form the compound KCl according to the equation above. What remains in the reaction vessel after equal masses of K(s) and Cl2(g) have reacted until either one or both of the reactants have been completely consumed?
Cr, Mn, Fe, Co
The elements in which of the following have most nearly the same atomic radius?
Oxidation-reduction, because H2(g) is oxidized
When C2H4(g) reacts with H2(g), the compound C6H6(g) is produced, as represented by the equation above. The reaction is correctly classified as which of the following types?
Using twice the volume of MgCl2(aq) and twice the volume of NaOH(aq)
MgCl2(aq)+2NaOH(aq)→2NaCl(aq)+ Mg(OH)2(s) A 100 mL sample of 1.0 M MgCl2(aq) and a 100 mL sample of 0.2 M NaOH(aq) were combined, and Mg(OH)2(s) precipitated, as shown by the equation above. If the experiment is repeated using solutions of the same molarity, which of the following changes would double the amount of Mg(OH)2(s) produced?
One-fifth the number of Fe2+ ions that are consumed
MnO4- + 5Fe2+ + 8H+ → Mn2+ + 5Fe3+ + 4H2O In the reaction represented above, the number of MnO4- ions that react must be equal to which of the following?
.160 M
A 20.0-milliliter sample of 0.200-molar K2CO3 solution is added to 30.0 milliliters of 0.400-molar Ba(NO3)2 solution. Barium carbonate precipitates. The concentration of barium ion, Ba2+, in solution after reaction is
CH5N
A sample compound that contains only the elements C, H, and N is completely burned in O2 to produce 44.0 g of CO2, 45.0 g of H2O, and some NO2. A possible empirical formula of the compound is
25%
Li3N(s) + 2H2(g) ⇄ LiNH2(s) + 2LiH(s) ΔH° = -192 kJ/molrxn Because pure H2 is a hazardous substance, safer and more cost effective techniques to store it as a solid for shipping purposes have been developed. One such method is the reaction represented above, which occurs at 200°C. When 70. g of Li3N(s) (molar mass 35 g/mol) reacts with excess H2(g), 8.0 g of LiH(s) is produced. The percent yield is closest to