CHM1 Review for Exam 12

Transcription

1 Topics Solutions 1. Arrhenius Acids and bases a. An acid increases the H + concentration in b. A base increases the OH - concentration in 2. Strong acids and bases completely dissociate 3. Weak acids and bases only dissociate to a small percentage. 4. Acids and bases as electrolytes 5. Neutralization reactions Acid + base salt + water 6. Autoionization of water a. H 2 O H + + OH - 7. Neutralization reactions molecular, ionic and net ionic reactions 8. ph and poh a. ph = -log [H + ] b. poh = -log [OH - ] c. ph + poh = 14 d. ph scale acidic, basic and neutral 9. Acid Base titrations a. Calculations b. Equivalence point c. Indicators and end points d. Titrations curves

2 Multiple Choice 1. Which of these ph numbers indicates the highest level of acidity? (1) 5 (3) 10 (2) 8 (4) According to the Arrhenius theory, when a base dissolves in water it produces (1) CO 3 2- as the only negative ion in (2) OH - as the only negative ion in (3) NH 4 + as the only positive ion in (4) H + as the only positive ion in 3. Which when mixed with a drop of bromthymol blue will cause the indicator to change from blue to yellow? (1) 0.1 M HCl (3) 0.1 M CH 3 OH (2) 0.1 M NH 4 OH (4) 0.1 M NaOH 4. What is the ph of a containing 20 grams of NaOH in 1000 milliliters of? (1) 0.30 (3) 0.30 (2) (4) What is the ph of a whose H + concentration is 1.5 M? (1) 0.18 (3) (2) 0.18 (4) A whose ph is 8.9 is (1) Acidic (2) Basic (3) Neutral 7. A student neutralized 16.4 milliliters of HCl by adding 12.7 milliliters of a M KOH. What was the molarity of the HCl? (1) M (3) M (2) M (4) M 8. When the ph of a changes from a ph of 5 to a ph of 3, the hydrogen ion concentration is (1) 0.01 of the original content (2) 0.1 of the original content (3) 10 times the original content (4) 100 times the original content 9. A sample of Ca(OH) 2 is considered to be an Arrhenius base because it dissolves in water to yield (1) Ca 2+ ions as the only positive ions in (2) H 3 O + ions as the only positive ions in (3) OH - ions as the only negative ions in (4) H - ions as the only negative ions in 10. Which reaction occurs when hydrogen ions react with hydroxide ions to form water? (1) substitution (3) ionization (2) saponification (4) neutralization 11. Which equation represents a double replacement reaction? (1) 2 Na + 2 H 2 O 2 NaOH + H 2 (2) CaCO 3 CaO + CO 2 (3) LiOH + HCl LiCl + H 2 O (4) CH O 2 CO H 2 O

3 12. Which of the following acids is a weak electrolyte? 16. Which of the following is a polyprotic acid? (1) HF (3) HNO 3 (2) HCl (4) HClO Which of these 1 M s will have the highest ph? (1) NaOH (3) HCl (2) CH 3 OH (4) NaCl 14. Given the following s Solution A: ph of 10 Solution B: ph of 7 Solution C: ph of 5 Which list has the s placed in order of increasing H + concentration? (1) A, B, C (3) C, A, B (2) B, A, C (4) C, B, A 15. A compound whose aqueous conducts electricity and turns phenolphthalein pink is (1) HCl (3) NaOH (2) HC 2 H 3 O 2 (4) CH 3 OH (1) NH 3 (3) H 3 PO 4 (2) HCl (4) CH Which of the following is a weak base? (1) ammonia (2) sodium chloride (3) calcium hydroxide (4) sodium hydroxide 18. Which of the following s would cause methyl orange to be red? (1) 0.10 M HCl (2) M NaOH (3) M Ca(OH) 2 (4) M HNO Which of the following, when dissolved in water would produce a neutral? (1) vitamin C (2) phosphoric acid (3) sodium chloride (4) potassium hydroxide 20. Which substance is an Arrhenius acid? (1) LiF (aq) (3) Mg(OH) 2 (aq) (2) HBr (aq) (4) CH 3 CH 2 OH (aq)

4 Short Answers Calcium hydroxide is commonly known as agricultural lime and is used to adjust soil ph. Before lime was added to a field, the soil ph was 5. After the lime was added, the soil underwent a 100-fold decrease in the hydrogen ion concentration. 21. What is the new ph of the soil in the field? 22. Calcium hydroxide is relatively soluble in water. Give the formula and name of another hydroxide compound that contains a Group Calculate the ph of the following s. You must show work to receive full credit. (a) 0.10 M HCl (b) M NaOH (c) a 0.35 M of a weak acid that dissociate 2%. (d) a 0.15 M of a weak base that dissociate 10%.

5 24. If an acid is added to an aqueous, briefly describe what happens to the ph and poh of the as compared with the original ph and poh of the. 25. A student recorded the following buret readings during a titration of 25.0 ml of a potassium hydroxide with unknown concentration with hydrochloric acid: Initial reading Final Reading Standard M hydrochloric acid 9.08 ml ml a. Write the balanced neutralization reaction. b. Calculate the molarity of the potassium hydroxide. Show all work.

6 26. Draw a plot of the titration curve of a 0.10 M hydrochloric acid is titrated with sodium a 0.10 M NaOH. Be sure to: (a) Put the ph on the y-axis and ml of NaOH added on the x-axis. (b) Use appropriate scales and label the axes. (a) Start the titration at the initial ph of the HCl (b) Label the equivalence point and make sure that it occurs at the appropriate ph and added volume of NaOH for this titration (c) Select an indicator from the reference table that could be used for the end point of this titration. (d) Write the balanced neutralization reaction

7 Answers the ph = Sr(OH) 2 or Ba(OH) (a) ph = 1.0 (b) ph = 12.0 (c) ph = 2.2 (d) ph = The ph will go down and the poh will go up. 25. (a) KOH (aq) + HCl (aq) KCl (aq) + H 2 O (l); (b) M 26. Show your teacher.