Science NLN practice questions

To be isotopes, two atoms of the same element must have a different number of (A) neutrons. (B) protons. (C) electrons. (D) quarks. - Answer- (A) neutrons. Depending on its environment, a substance that can act as either an acid or a base is described as (A) amphoteric. (B) an isomer. (C) hydrolytic. (D) a polymer. - Answer- (A) amphoteric. A certain substance is not broken down in a chemical reaction. The substance is most likely (A) a compound. (B) an aqueous solution. (C) an element. (D) a heterogeneous mixture. - Answer- (C) an element. A hydrogen ion concentration of 1 × 10−7 M in a solution is considered (A) basic. (B) alkali. (C) acidic. (D) neutral. - Answer- (D) neutral. The radioactive isotope I-131 has a half-life of 8 days. What fraction of a sample of I-131 will remain after 24 days? (A) 1⁄4 (B) 1⁄16 (C) 1⁄8 (D) 1⁄2 - Answer- (C) 1⁄8 Which of the following particles/rays is not a type of radioactive emanation? (A) alpha particle (B) beta particle (C) gamma ray (D) carbon-12 - Answer- (D) carbon-12 The