Chem A Final Exam Review In-class problem-solving

1. Determine the oxidation state of S in HSO 3 -. Set your equation equal to -1 since this is a -1 ion. Assign the most electronegative atom first. In this problem it is O. O usually has an oxidation state of -2. Since there are 3, total = -6. Assign H next. H usually has an oxidation state of +1. S must be +4. (+1) + (+4) + (-6) = -1

2. What are the products of the reaction between LiOH and HF? What type of reaction is this? Neutralization reaction. Water and salt (LiF) LiOH + HF  H 2 O+ LiF

3. How many grams of NaOH should be added to 225g of water to produce a 0.10m solution? m = mol of solute/kg of water 0.1 = x/.225 X =.0225 mol.0225 mol X g/mol =.90g

4. How many unpaired electrons are in the ground state of oxygen? = 2 unpaired electrons Electron configuration = 1s 2 2s 2 2p 4 Electron dot = O

5. Which demonstrates the trend for increasing atomic radius? a. Li; Na; Korb. Ba; Sr; Ca a. Atomic radius increases as you move down a family.

6. What is the difference between: Boiling/condensation Sublimation/deposition Melting/freezing

Solid LiquidGas deposition sublimation condensation freezing evaporationmelting Endothermic processes Exothermic processes

Heat curve – be able to label! Solid Boiling (l  g) Melting (s  l) Liquid Gas

7. Add 5.47 g, 4.2 cg and 5.39g 1. Be sure to convert so all units are the same. 2. This is a significant figure problem. When adding or subtracting look at places past decimal. 5.47g +.042g g =10.90g

8. What is the total number of ions in 2.0 mol Cu(NO 3 ) 2 ? 2 mol X (3 ions/1 mol) x (Avogadro’s #/1 mol) = 3.6 x ions

9. What is the correct formula for magnesium sulfate? Reminders: Write the charges of ions The sum of the charges must equal 0 for a neutral compound Magnesium cation = 2+ sulfate anion= 2- Need one of each OR Write charges and use criss-cross rule. Like charges cancel out. Remember to reduce if able Answer = MgSO 4

10. Write a balanced equation of the reaction between aluminum sulfate and calcium hydroxide. Al 2 (SO 4 ) 3 + 3Ca(OH) 2  2Al(OH) CaSO 4

11. What is the empirical formula for C 4 H 10 ? Empirical formula = simplest whole- number ratio C 2 H 5

12. A 5.0 L of krypton gas is at a pressure of 765 mmHg. At constant temperature what volume will the gas occupy if the pressure decreases to 700. mmHg? Boyle’s Law = P 1 V 1 = P 2 V 2 ; (765)(5.) = (700.) (x) = 5.5 L

13. Use the following equation: Fe 2 O 3 + CO  Fe + CO 2 What mass of Fe is formed from 1800g of Fe 2 O 3 ? Answer = 1300g Fe (sig figs) 1. Balance equation. 2. Must have a mole:mole ratio 3. In order to achieve this you must use molar masses to convert to moles 4. Fe 2 O 3 + 3CO  2 Fe + 3CO 2

14. How many oxygen atoms are present in iron (II) sulfate octahydrate FeSO 4.8H 2 O 4 O in iron (II) sulfate 8 O in water Add! = 12 O The dot just means water can be removed – do not multiply!

15. How many liters of H 2 O (g) at STP will react with one mole of H 2 S? H 2 S + O 2  H 2 O + SO 2 Balance equation! 2H 2 S + 3O 2  2H 2 O + 2SO 2 Use 22.4 L = 1 mol Answer = 22.4 L

16. A sample of ethanol required 25 kJ of energy to be heated from 20.°C to 28°C. How many grams of ethanol were heated? Ethanol C p = 3.42 J/g.°C. Q = (m)(∆T)(C p ) 25000J = (m)(8)(3.42) m = 914g

17. A weak base is titrated with a known concentration of a strong acid. Sketch the titration curve. Based on equivalence point. Above 7 = strong base/weak acid At 7 = strong base/strong acid Below 7 = weak base/strong acid Graph on next slide

Titration curve weak base/strong acid Starting Solution: weak base Added Standard: strong acid 14 7 equivalence point (below 7)

18. Choose the series of elements that increases in electronegativity. a. Rb, Cs, Frb.N, O, F B. Remember atomic radius! Decreases as you go left to right, increases as you go down. All other trends are opposite!!!

19. Calculate p +, n 0, and e - in S 2-. Sulfur Atomic # = 16 Atomic mass = 32 proton # = Atomic # =16 Neutron# = Mass # - Atomic # = 16 Electrons = protons in a neutral atom. Add 2 electrons to make this ion = 18 electrons

20. Is HSO 4 - acting as an acid or a base in this equation? HSO H 2 O ↔ SO H 3 O + HSO 4 - is the acid because it donates a hydrogen ion (H+)

21. What is the atomic average atomic mass of the following isotope? Atomic Mass% Abundance Multiply each mass by abundance (move decimal 2 places to left) Add your product – do NOT divide by 3! Answer = 27

22. The half-life for candium = 100 years. If 12.5% of a sample remains, how old is the candium sample? 3 half-lives go by Sample is 300 years old

23. Write the Ksp expression for Iron (II) nitrate (s). Ksp = [Fe 2+ ][NO 3 - ] 2

24. What is the H for the reaction A  B? (see diagram on board) Reminders: Products – Reactants If products have more energy than the reactants, the value is positive and the reaction is endothermic. If the products have less energy than the reactants, the value is negative and the reaction is exothermic.

25. A compound is 36.5% sodium, 25.4% sulfur, and 38.1% oxygen. What is the empirical formula? If the molecular mass is 252, what is the molecular formula? % to mass Mass to moles Divide by smallest Multiply until whole = Na 2 SO 3

26. Describe how you would determine the density of cube of copper 1.0 cm on each side? How would determining density of an irregular object differ? D = mass/volume L x w x h = volume; then mass object Mass the object and then use a graduated cylinder to determine water displacement.

27. Calculate [H 3 O + ] for a substance with a pH of 5.7. [H 3 O] = 10 -pH = 2.0 x 10 -6

28. What is the pH and pOH of a solution if the [H 3 O + ] is 3.4 x M? pH = -log[H 3 O + ] pH = 4.5 pH + pOH = 14 pOH = 9.5

29. Mineral oil dissolves in canola oil but does not dissolve in water. What is the reason for this? “like dissolves like” Polar solutes dissolve in polar solvents and nonpolar solutes dissolve in nonpolar solvents Water is a known polar compound The oils must be non-polar.

30. Name the following: H H H H H H H-C - C - C-HH-C = C -C-H H H H H Propane – 3 carbons, all single bonds Propene – 3 carbons, 1 double bond

31What is the molecular geometry of the following? a.BF 3 b. CH 4 c. NH 3 a. = trigonal planar b.= tetrahedral c. = trigonal pyramidal FB FH F HCHN HHHH

32.Which has a greater effect on the melting point of ice? a.MgBr 2 b. CH 2 H 5 OHc. KCl a. Dissociation factor is 3. the d.f. in b is one and the d.f. in c is 2. in equal amounts, magnesium bromide will have the greater effect.

33.Which molecule is nonpolar? a.CO 2 b. NaClc. NH 3 Carbon dioxide

34.What particle is omitted when Po-210 changes to Pb- 206? alpha

35.How many moles are in 236 g of NaOH? 5.90 moles

36.What is the IUPAC name for Ni 3 (PO 4 ) 2 ? Nickel (II) phosphate

37.How many grams of Na are in 56 g of NaOH? 22.99/40.00 X 56g = 32 g

38.Consider the following reactants: Cu(NO 3 ) 2 (aq) + Zn (s)  Predict products Balance equation What is the oxidizing agent? Cu(NO 3 ) 2 (aq) + Zn (s)  Zn(NO 3 ) 2(aq) + Cu (s) OIL RIG Zn must lose electrons to form ion so it is being oxidized. Cu 2+ is oxidizing agent