Science MCQs

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

  • A. Hg(l) → Hg22 (aq)
  • B. Fe2 (aq) → Fe3 (aq)
  • C. NO3-(aq) → NO(g)
  • D. SO32-(aq) → SO42-(aq)
  • Correct Answer: Option D

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

  • A. NH2-
  • B. NH3
  • C. H
  • D. NH4
  • Correct Answer: Option B

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

  • A. H - O bonds break as H - H and O - O bonds form.
  • B. Hydrogen bonds between H2O molecules are broken.
  • C. Covalent bonds between H2O molecules are broken.
  • D. Ionic bonds between H ions and OH- ions are broken.
  • Correct Answer: Option B

When 100 mL of 1.0 M Na3PO4 is mixed with 100 mL of 1.0 M AgNO3, a yellow precipitate forms and [Ag ] becomes negligibly small. Which of the following is a correct listing of the ions remaining in solution in order of increasing concentration?

  • A. [PO43-] < [NO3-] < [Na ]
  • B. [PO43-] < [Na ] < [NO3-]
  • C. [NO3-] < [PO43-] < [Na ]
  • D. [Na ] < [NO3-] < [PO43-]
  • Correct Answer: Option A

K(s) ½ Cl2(g) → KCl(s) ΔH° = -437kJ/molrxn The elements K and Cl react directly to form the compound KCl according to the equation above. Refer to the information above and the table below to answer the questions that follow. 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?

  • A. KCl only
  • B. KCl and K only
  • C. KCl and Cl2 only
  • D. KCl, K, and Cl2
  • Correct Answer: Option C

What mass of Au is produced when 0.0500 mol of Au2S3 is reduced completely with excess H2?

  • A. 9.85 g
  • B. 19.7 g
  • C. 24.5 g
  • D. 39.4 g
  • Correct Answer: Option B

W(g) X(g) → Y(g) Z(g) Gases W and X react in a closed, rigid vessel to form gases Y and Z according to the equation above. The initial pressure of W(g) is 1.20 atm and that of X(g) is 1.60 atm. No Y(g) or Z(g) is initially present. The experiment is carried out at constant temperature. What is the partial pressure of Z(g) when the partial pressure of W(g) has decreased to 1.0 atm?

  • A. 0.20 atm
  • B. 0.40 atm
  • C. 1.0 atm
  • D. 1.2 atm
  • Correct Answer: Option A

NH4NO3(s) → N2O(g) 2 H2O(g) A 0.03 mol sample of NH4NO3(s) is placed in a 1 L evacuated flask, which is then sealed and heated. The NH4NO3(s) decomposes completely according to the balanced equation above. The total pressure in the flask measured at 400 K is closest to which of the following? (The value of the gas constant, R, is 0.082 L atm mol-1 K-1.)

  • A. 3 atm
  • B. 1 atm
  • C. 0.5 atm
  • D. 0.1 atm
  • Correct Answer: Option A

In which of the following species does sulfur have the same oxidation number as it does in H2SO4?

  • A. S2O32-
  • B. S2-
  • C. S8
  • D. SO2Cl2
  • Correct Answer: Option D

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

  • A. 0.20 g of H2
  • B. 0.40 g of H2
  • C. 3.2 g of O2
  • D. 4.0 g of O2
  • Correct Answer: Option A