"Unit 3 Review - Chemistry"
Unit 3 Review - Chemistry Name: ________________ Accuracy and Precision Complete pg 10 in VG Workbook 1. Averages: A – 10.29 B – 10.24 C – 12.04 D – 10.66 2. Percent error A – 0.49% (10.29 – 10.24) / 10.24 x 100 B – 0% C – 17.6% D – 4.1% 3. Average deviation – For each data point, find out how far it is from the average Example for A: Average for A was 10.29 Data points were 10.26, 10.30, 10.21, and 10.39 10.26 is 0.03 away from avg 10.30 is 0.01 away 10.21 is 0.08 away 10.39 is 0.10 away Avg of 0.03, 0.01, 0.08, and 0.10 is 0.0675 A – 0.0675 B – 0.46 C – 0.0175 D – 1.32 4. Best to worst accuracy (which students were closest to the right answer). This is determined by who has the lowest % error. B is best, then A, D, C is worst 5. Best to worst by precision (which students were the most consistent). This is determined by who has the lowest average deviation. C is best, then A, B, D is worst Metal, Nonmetal, or Semimetal Use the clues to determine if the following are metals (M), nonmetals (NM), or semimetals (SM) 1. Malleable and conducts electricity M 2. Brittle and shiny SM – Brittle is like nonmetal, shiny is like a metal 3. Ductile and a good heat conductor M 4. Gas at room temperature NM 5. Sulfur NM 6. Cobalt M 7. Arsenic SM 8. Plutonium M 9. Dull and a good conductor of electricity SM 10. Usually solid at room temperature M 11. Gains electrons to be stable NM 12. Malleable and breaks down in acid M 13. Polonium SM 14. Fluorine NM 15. Technetium M 16. Samarium M Percent Composition 17. What is the % of Br in MgBr2? 159.8/184.11 x 100 = 86.8% 18. What is the % of O in Al(OH)3? 48/78.01 x 100 = 61.53% 19. What is the % of S in Ga2(SO4)3? 96.21/427.65 x 100 = 22.5% 20. If you are mining for iron, what is a better source: FeO or Fe2O3? Show work. FeO is a better source because it contains a higher % of Fe. Even though Fe2O3 appears to have more Fe, is has even more O which gets in the way. FeO - 77.7% Fe Fe2O3 – 69.9% Fe Periodic Trends/Groups Determine which atom is larger in size (not necessarily mass) 21. Mg or P Mg – further to left, same number of shells, but fewer protons 22. S or As As – further to bottom left, more shells 23. Li or He Li – further to bottom left, more shells 24. Cr or Eu Eu – further to bottom left, more shells (remember that the part of the table where Eu is actually belongs in the part of the table where La and Ac are) 25. Mg or Mg2+ Mg – Mg has more electrons and so is bigger 3- 26. N or N N3- - N3- has more electrons and therefore is bigger Determine which atom is more reactive 27. Na or K K – it’s a metal so further down and to the left on table is more reactive (farther from boundary – also, K is larger and larger atoms lose electrons more easily, which is how metals react) 28. P or O O – it’s a nonmetal so further up and to the right is more reactive. This makes it a smaller atom and smaller atoms gain electrons more easily, which is how nonmetals react. 29. Fe or Cu Fe – they’re metals and so further down and to the left is more reactive 30. S or He S – Helium is “disqualified” because it is a noble gas and they don’t react Identify the element based on the clues 31) Element in third period with 4 valence electrons Si 32) Metalloid in second period B 33) Heaviest alkaline earth metal Ra 34) 4th period and forms –2 charge Se 35) Alkali metal that is smallest in size Li – H doesn’t count as alkali metal 36) Halogen that is largest in size At 37) 5th period semimetal that is larger in size Sb 38) Noble gas that is largest in size Rn 39) Lightest noble gas He 40). Heaviest 3rd period element Ar (heaviest is not same as biggest 41) Largest transition metal Ac (or whatever metal is on the bottom left of your table where the transition metals are – this can vary by table) 42) Smallest atom on table He 43) Most reactive alkali metal Fr 44) Most reactive halogen F 45) Least reactive alkaline earth metal Be 46) Most reactive metal in 5th period Rb Balancing Equations – Balance the following equations 47) 2 HgO ---> 2 Hg + O2 48) 8 H2S + 8 Cl2 ---> S8 + 16 HCl 49) SrBr2 + (NH4)2CO3 ---> SrCO3 + 2 NH4Br 50) Al2(SO4)3 + 3 Ca(OH)2 ---> 2 Al(OH)3 + 3 CaSO4 51) 2 C6H14 + 19 O2 ---> 12 CO2 + 14 H2O