18) Express 0.000 000 000 000 1 in exponential form. A) 1 × 10-13 B) 1 x 10-12 C) 1 × 10-1 D) 1 x 1013 E) none of the above 19) One milliliter of helium gas contains 26,900,000,000,000,000,000 atoms at normal temperature and pressure. Express this number of atoms in scientific notation. A) 2.69 x 1017 B) 2.69 x 1018 C) 2.69 x 1019 D) 26.9 x 1018 E) 26.9 x 1019 20) If a marathon race is 26.2 miles, what is the distance in yards? (Given: 1 mile 1760 yards) A) 0.0149 yards B) 67.2 yards C) 46,000 yards D) 46,100 yards E) 46,110 yards 21) A sample of rose gold is: 12.0 grams gold, 5.0 grams silver, and 7.0 grams copper by mass. What is the percent copper in the sample? A) 12% B) 29% C) 50% D) 58% E) 75% 22) Subtract 9.0 × 103 from 2.0 x 104 and express the answer in scientific notation. A) 1.1 × 101 B) 1.1 × 102 C) 1.1 × 103 D) 1.1 x 104 E) 1.1 × 105