Science NLN practice Questions and Answers with complete solution

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 strongest acid can be found in which of the following pH ranges? (A) 11.1−12 (B) 7.1−8.2 (C) 4.5−5.7 (D) 1.0−2.0 - Answer-(D) 1.0−2.0 The symbol K on the periodic table stands for (A) potassium. (B) calcium. (C) carbon. (D) phosphorus. - Answer-(A) potassium. Which of the following reactions releases heat energy? (A) double replacement (B) decomposition(C) endothermic (D) exothermic - Answer-(D) exothermic Which gas law states that the volume of a gas is inversely proportional to the pressure? (A) Ideal Gas Law (B) Boyle's Law (C) Combined Gas Law (D) Charles' Law - Answer-(B) Boyle's Law