UNIT 4 TEST AP CHEM

Which of the following particulate diagrams best shows the formation of water vapor from hydrogen gas and oxygen gas in a rigid container at 125*C?

(C) Six big molecules Ten little molecules combine to make Five big molecules

The diagrams above represent pollutes present in two different dilute aqueous solutions before they were mixed water molecules are not shown . When the solutions were combined a precipitation reaction took place. Which of the diagrams below is the best particle representation fo the mixture after the precipitation reaction occurred?

(D) Ag and Cl at bottom and Na and NO3 floating around the top of picture.

At 20.0 - milliliter sample of 0.200-molar K2Co3 solution is added to 30.0 milliliter of 0.400-molar Ba(NO3)2 solution.Barium carbonate precipitates. The concentration of barium ion, Ba2+, in solution after reaction is?

0.160 M

If 0.40 mol of H2 and 0.15 mol of O2 were to react completely as possible to produce H2O, what mass of reactant would remain?

0.20 g of H2

A reaction in which the same reactant undergoes both oxidation and reduction?

3Br2(aq) + 6OH-(aq) --> 5 Br (aq) + BrO3- (aq) + 3H2O(l)

According to the balanced equation above, how many moles of HI would be necessary to produce 2.5 mol of I2 starting with 4.0 mol of KMnO4 and 3.0 mol of H2SO4?

5.0

A precipitation reaction

Ca2+(aq) + SO42-(aq) --> CaSO4 (s)

Which of the following is the net ionic equation for the reaction between aqueous sodium fluoride and hydrochloric acid?

F-(aq) + H+(aq) --> HF(aq)

Which of the following describes the changes in forces of attraction that occur as H2O changes phase from a liquid to a vapor?

Hydrogen bonds between H2O molecules are broken.

Which of the following is the conjugate acid of NH2-?

NH3

NH3(aq) + HCl(aq) --> <-- NH4+(aq) + Cl-(aq) The Bronsted-Lowry bases in the reaction represented above are?

NH3(aq) and Cl-(aq)

Which of the following represents a process in which a species is reduced?

NO3-(aq) --> NO(g)

At 127* C the entire sample of I2 is observed to have vaporized. How does the mass of vessel 5 at 127* C compare to its mass at 27* C?

The mass is the same, since the number of each type of atom in the vessel is constant.

H2Se(g) + 4O2F2(g) --> SeF6(g) + 2HF(g) + 4O2(g) Which of the following is true regarding the reaction above?

The oxidation number of Se changes from -2 to +6

A 100mL sample of 0.1 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 in volume will double the amount of Mg(OH)2 (s) produced?

Using twice the volume of MgCl2 (aq) and twice the volume of NaOH(aq).