June 2017 Chemistry Regents #31-35
Highlight to reveal answers and explanations
| ||||||||||||
Questions | Answer | Links | Explanations | |||||||||
31. Which electron configuration represents the electrons of an atom of neon in an excited state? (1) 2-7 (3) 2-7-1 (2) 2-8 (4) 2-8-l | 3 | link | neon has a ground state configuration of 2-8 excited states have the same number of electrons, but in a higher energy level 2-7-1 | |||||||||
32. Which numerical setup can be used to calculate the atomic mass of gallium? Natural Abundance of Two Gallium isotopes
(1) (0.60ll)(68.926 u) + (0.3989)(70.925 u) (2) (60.11)(68.926 u) + (39.89)(70.925 u) (3) (0.60ll) (70.925 u) + (0.3989)(68.926 u) (4) (60.11)(70.925 u) + (39.89)(68.926 u) | 1 | link | atomic mass is a weighted average at. mass= (mass x % (as a decimal)) + ( mass x % as a decimal) | |||||||||
| 33. A student measures the mass and volume of a sample of copper at room temperature and 101.3 kPa. The mass is 48.9 grams and the volume is 5.00 cubic centimeters. The student calculates the density of the sample. What is the percent error of the student's calculated density? (l) 7.4% (3) 9.2% (2) 8.4% (4) 10.2% | 3 | link | density=m/v=48.9g/5.00cm^3 d=9.78g/cm^3 accepted is on the RT table S=8.96g/cm^3 %error=(measured-accepted)/accepted x 100% % error= (9.78-8.96/8.96) * 100% | |||||||||
| ||||||||||||
34 What is the chemical formula for sodium sulfate? (1) Na2SO4 (3) NaSO4 (2) Na2SO3 (4) NaSO4 | 1 | link | Sodium is Na+ Sulfate is SO42- Na2SO4 | |||||||||
35 Given the balanced equation representing a reaction: 2Na(s) + Cl2 (g) --> 2NaCl(s) + energy If 46 grams of Na and 71 grams of Cl2 react completely, what is the total mass of NaCl produced?(1) 58.5g (3) 163g (2) 117g (4) 234g | 2 | Law of conservation of mass mass in = mass out 46g + 71 in = X out
| ||||||||||
| ||||||||||||