Chapter 9

The following volumes of 0.000300 M SCN- are diluted to 15.00 mL. Determine the concentration of SCN- in each sample after dilution. These values will be used during the experiment.  Sample 0.000300 M SCN- (mL) [SCN-] (M) 1  1.50   2 3.50   3 7.00   4 10.00

Identify the type of error (systematic or random) for each of the following situations below and defend your answer briefly: The student forgot to obtain the mass of the filter paper before filtering the solution and calculating the mass of the precipitate. a. b. In the water analysis, trial 3 was analyzed 2 days after the analysis of trials 1 and 2. Experiment #2 was conducted from 8:00 AM to 4:00 PM. The weather at the start of the experiment was sunny then became rainy with thunderstorms after 12 NN. C. d. The NaOH solution used by the students in the titration of vinegar was expired

Consider the following reactions that take place in aqueous solution and related information.H2CO3 + HS- ⇋ H2S + HCO3-HSO4- + HCO3- ⇋ H2CO3 + SO4 2-H2CO3 (Ka1 = 4.2x10-7, Ka2 = 4.8x10-11) H2S (Ka1 = 1x10-7, Ka2 = 1x10-19) H2SO4 ( Ka1 = Very Large, Ka2 = 1.2x10-2)What is the strongest base in the reactions given?

2 20 E Solid silver fluoride is slowly added to 150 mL of a potassium chromate solution until the concentration of silver ion is 0.0538 M. The maximum amount of chromate remaining in solution is C Submit Answer $ 4 R FI F V Retry Entire Group 8 more group attempts remaining % Use the References to access important values if needed for this question. 5 T Cengage Learning | Cengage Technical Support G ^ 6 B MacBook Pro Y H & N 20 7 U N ▶II * 00 8 J I M ( 9 K O V. ) O < L ✔ M. P A Previous Email Instructor + Next Save and Exit 21 ?

L.O Page View Read aloud V Draw A Highlight Erase A chemist tries to dissolve a solid ionic compound called "X" in water at 25°C. He adds 100 mL of water to a beaker equipped with a stirrer on a balance. While slowly adding X to the beaker, he measures the mass of X added and, at the same time, carefully watches to make sure that everything he adds dissolves. Suddenly, when he has just added a total of 2 g of X, he sees that the mixture is no longer homogeneous (i.e. some of the X remains on the bottom of the beaker and won't dissolve). He divides the 2 g of X by the 100 mL of water and obtains the value 0.02 g X/mL water. This number répresents an important physical property of X. What is it uniquely called? A) the molarity of X in water at 25°C B) the concentration of X in water at 25°C C) the mass of X in water at 25°C D) the density of X in water at 25°C E) the solubility of X in water at 25°C How would you describe the solution that the chemist prepared in Question#1? A)…

1- Perform the activity (Home Made Indicator) on page 138 of your textbook. Activity 2- Prepare three cups one contains vinegar, the second contains salt solution and the third contains clorox solution. Tabulate your observations. Solution Vinegar Salt solution Clorox solution Color after adding indicator 3- To a cup containing chalk or egg shell add few ml of vinegar. Record your observation. Observation Reactants Products Word Equation

Name Chem Section Data Sheet determination 23°C 23°C 25°C temperature of filtered KHT solution, °C 0.04m concentration of NaOH solution, mol L- 0.04 m 0.04m KHT solution 14.9 49-5 final buret reading, mL initial buret reading, mL 49.9 volume of KHT used, mL NaOH solution 28 final buret reading, mL 10 49.8 १.१ 49.7 initial buret reading, mL 50 40mL volume of NaOH used, mL number of moles of NaOH used 0014 0014 number of moles of HT titrated .04 [HT] in KHT solution, mol L- 1.42 1.142 1.142 [K*] in KHT solution, mol L-1 solubility of KHT, mol L-1 average solubility of KHT, mol L- Ksp average Ksp

Heroin and morphine (shown below) are odorless solids. Drug-sniffing dogs can sometimes locate heroin that has been exposed to the elements because of a strong odor that is present in small quantities. What compound causes the odor and suggest what reaction is responsible for the compound's formation. H3C. но reaction? odor compound? 'N. CHз CHз H3C но herion morphine

7. What mass of silver chloride will be recovered if excess sodium chloride is added to 500 mL of solution containing 10.79 g of Ag*? 10.8 g b. 21.6 g 28.6 g d. 7.2 g 14.3 g а. е. с.

Pre-Lab Questions 1. Explain the benefit of letting the solutions of HCl(aq) and NaOH(aq) sit overnight. 2. When using the same graduated cylinder to measure the volumes of HCl(aq) and NAOH(aq), it is important to rinse the cylinder with water and a small amount of the second reactant before measuring the volume of the second reactant. Explain why this is important for this investigation. 3. Describe how to perform each of the following safely: • diluting a strong acid solution with water • dissolving a solid base in water • adding a solution of base to a solution of acid 4. If acid comes in contact with your skin, why must you flush the area with plenty of cold water, rather than neutralizing the acid with a base?

Suppose a pair of chemical compounds A and B can react in two different ways: A+BC Reaction 1 gives product C. A+B D Reaction 2 gives product D. The following facts are known about the two reactions: • Reaction 1 is endothermic and Reaction 2 is exothermic. • If a reaction vessel is charged ("filled") with A and B, then at first D is produced faster than C. Use these facts to sketch a qualitative reaction energy diagram for both reactions. Note: because these sketches are only qualitative, the energies don't have to be exact. They only have to have the right relationship to each other. For example, if one energy is less than another, that fact should be clear in your sketch. Reaction 1 Reaction 2 energy energy A + B A + B reaction coordinate reaction coordinate Explanation Check 2021 atcGre Educalion. All Rights feserved earch hp

A student removes 25 mL of 3.0 M NaOH and dilutes it to final volume of 350 mL. What is the concentration of the resulting solution.? 48. А. 42 M В. 0.024 M С. 75 M D. 0.10 M E. 0.21 M

CONCENTRATION DETERMINATION Buret contains NaOH solution *Sodium hydroxide solution: To 1 part reagent grade NaOH add 1 part distilled, carbon dioxide-free water by weight Erlenmeyer flask contains about 9ml of the acid and about 10 ml of distilled water made recently free from CO2 by boiling. DATA SHEET II Final Reading HCI Initial Reading HCI 9.4 Final Reading NaOH Initial Reading NaOH 10.65 10.55 1 ml HCI 1 mL NAOH mL NAOH mL NaOH mL HCL mL HCL Mean Values: 1 ml HCI = 1 mL NaOH = _mL NaOH mL HCL COMPUTATION:

Two students are studying the Arrhenius reaction below: NAOH + Hz S04 acid → Na SOy + HzO base salt water Did the students identify the acid, base and salt correctly? If not, provide the correction.

Which of the following substances has the highest concentration of hydroxide ion in balance with water? H2O (Kw x 1.00 x 10-14) HX (Ka x 2.2 x 10-8) HY (Ka x 4.4 x 10-7) HO2Y (Ka x 2.2 x 10-9) TODAY (Ka x 4.4. x 10-10)

Complete the following table, making sure to include your units! Concentration of Concentration of acetic acid Water level on measuring cylinder before reaction 98 mL 91 mL 95 mL 0.5% 0.2% 0.1% ● sodium bicarbonate 0.5 M 0.5 M 0.5 M From the results above, which reactant do you consider to be the limiting reagent? Why? ● Water level on measuring cylinder after reaction 8 mL 49 mL 81 mL Consider the reaction where the concentration of acetic acid was 0.5% and the concentration of sodium bicarbonate was 0.5 M. Complete the table on page 5 to calculate the theoretical yield of CO2 with these concentrations. The following bullet points may help: You have already calculated the amount of sodium bicarbonate in 100 mL In a 100 mL solution of acetic acid at 0.1% there will be 0.1 mL of acetic acid. ● Volume of gas produced The density of acetic acid is 1.05 g/mL. You can use this value to calculate the mass of acetic acid used in the reaction.

7. A student weighs out exactly 1.562 grams of p-aminophenol and exactly 40 mL of water. After dissolving p-aminophenol in HCI, 10 mL of acetic anhydride is added. The student follows the procedure and acetaminophen is prepared. What is the maximum amount of acetaminophen she could obtain from the reaction if the percentage yield is 76%? I

Answered - Incorrect 1 attempt left Resubmit Question 6 Homework Unanswered Determine the molar concentration of Cl lons in 2.59E-1 M CaCiz(aq). Respond with the correct number of significant figures in scientific notation (Use E notation and only 1 digit before decimal eg 2.5ES for 2.5x 10) Type your numeric answer and submit 1. Submit Unanswered 3 attempts left

Report sheet for Titration of vinegar   Part I:  Standardization of the NaOH solution with KHP                                                                                      Trial 1               Trial 2               Trial 3                          Mass of Erlenmeyer flask + KHP (g)                                   78.34               78.27               78.01 Mass of empty flask (g)                                                  77.12               77.12               77.12 Mass of KHP (g)                                                                1.22              1.15                 0.89    Final buret reading (mL)                                                31.35               30.53               27.71               Initial buret reading (mL)                                              16.35               15.78               14.20               Vol NaOH solution delivered (mL)…

4. A student performs the HCl tests on the three solid samples as described in Step 5 of Part B and gets the same result for the solid CaCO3 sample and the mixture. Which of the following statements is true concerning these results? a. The results are to be expected. b. The results are not expected and could have been caused by using contaminated HCl. c. The results are not expected and could have been caused by using contaminated samples. Explain your answer.

1. Place a few crystals of bismuth trichloride in a test tube and add 3 ml of water. Observations: What change takes place? Write the equation for the reaction. Test the solution with litmus paper. What is the result? What causes this change? Add to the solution concentrated hydrochloric acid (CAUTION: CONCENTRATED HYDROCHLORIC ACID IS CORROSIVE AND CAN BURN THE SKIN!) a drop at a time with constant shaking until a change is observed. Observations: Give the effect of the following on the direction of the reversible reaction: a) adding more water: b) adding more HCl:

Which process could not be an electrolytic reaction?     a. 2 PbSO4(s) + 4 H2O(l)  Pb(s) + PbO2(s) + 2 H2SO4(aq)   b. 2H2O(l)  2H2(g) + O2(g)   c. 2Al2O3(l)  4Al(l) + 3O2(g)   d. Na+(aq) + Cl−(aq)  2Na(l) + Cl2(g)   e. 2Fe(s) + 3O2(g)  Fe2O3(s)

If the initial volume reading for the second titration was 0.76 mL and the final volume reading was 11.73 mL, what volume of iodine solution was used in your second titration (in mL)? Include the unit and two decimal places in your answer.