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Chaptr 4 HW Packet—Answer Key Multiple Choice—1 Point; Calculations—Three Points Unless Otherwise Specified—1 for Formula, 1 for Substitution, 1 for Calculation

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Chaptr 4 HW Packet—Answer Key Multiple Choice—1 point; Calculations—three points unless otherwise specified—1 for formula, 1 for substitution, 1 for calculation. 1. An unknown substance dissolves readily in water but not in benzene (a nonpolar solvent). Molecules of what type are present in the substance? a) nonpolar b) none of these c) neither polar nor nonpolar d) polar e) either polar or nonpolar Remember that “it’s all about interparticle forces.” In order for a solute to be able to mix in a liquid, the particles of the liquid have to be able to exert forces of attraction on the particles of the solute, breaking the interparticle forces of the solute, and then, to keep the particles of solute from reconnecting, the particles of solvent have to form bonds with the solvent particles that are more stable than the bonds between the solvent particles themselves. If a solute can dissolve in water, which is polar, the solute must therefore either be polar or ionic, because these are the types of substances with which water can develop forces of attraction. Benzene, which is non- polar, will not be able to develop forces of attraction with polar or ionic substances, and therefore, cannot dissolve these types of substances. In this list of answers, the substance must therefore be polar. Answer D (1 point/1) 2. The interaction between solute particles and water molecules, which tends to cause a salt to fall apart in water, is called a) dispersion b) coagulation c) hydration d) polarization e) conductivity The action of polar water molecules being able to develop forces of attraction with particles of ionic solids, and then being able to surround individual ions with a number of water particles that effectively separates the solute particles and keeps them mixed with the water particles is called hydration. Answer C (1 point/2) 3. Consider two organic molecules, ethanol and benzene. One dissolves in water and the other does not. Why? a) They have different molar masses. b) One is ionic, the other is not. Copyright © Cengage Learning. All rights reserved. Chapter Error! Unknown document property name.: Error! Unknown document property name. 70 c) One is an electrolyte, the other is not. d) Ethanol contains a polar O–H bond, and benzene does not. e) Two of these are correct. Again, in order for a solute to be able to mix in a liquid, the particles of the liquid have to be able to exert forces of attraction on the particles of the solute, breaking the interparticle forces of the solute, and then, to keep the particles of solute from reconnecting, the particles of solvent have to form bonds with the solvent particles that are more stable than the bonds between the solvent particles themselves. If a solute can dissolve in water, which is polar, the solute must therefore either be polar or ionic, because these are the types of substances with which water can develop forces of attraction. Because of its –OH group, ethanol is polar and can therefore dissolve in water. Benzene, which is entirely hydrocarbon, is non-polar and will not be able to dissolve in water. (a) Although the substances have different molar masses, and this could potentially play a role in solubility, in this case it does not. (b) Both substances are covalent so neither substance is ionic. (c) Because neither substance can dissociate into ions neither substance is an electrolyte. (d) Ethanol does contain a polar –OH bond while benzene does not and this is why, as explained above, ethanol can dissolve while benzene cannot. (e) only one answer suffices. Answer D (1 point/3) 4. T F Polar molecules have an unequal distribution of charge within the molecule. The reason that some molecules are polar is because there is an unequal distribution of charge within the molecule. Remember that this is due to differences in electronegativity between the atoms forming covalent bonds. Answer True (1 point/4) 5. Which of the following is a strong acid? a) HF b) HClO c) HBrO d) KOH e) HClO4 You should have memorized the six “strong” acids—those that can completely dissociate in water—memorizing these six means that anything else that is not one of these is a weak acid. They are HCl, HBr, HI, H2SO4, HNO3, HClO4. Therefore, (a) HF (hydrofluoric acid) ), as stated above, is not one of our six strong acids and so is a weak acid. (b) HClO (hypochlorous acid) is not HClO4—as stated above, it is not one of our six strong acids and so is a weak acid.. (c) HBrO (hypobromous acid) is not HBr— as stated above, it is not one of our six strong acids and so is a weak acid.. (d) KOH Copyright © Cengage Learning. All rights reserved. Chapter Error! Unknown document property name.: Error! Unknown document property name. 71 (potassium hydroxide) is a strong base. (e) HClO4 is one of our strong acids. Answer E (1 point/5) 6. All of the following are weak acids except a) HCNO b) HBr c) HF d) HNO2 e) HCN You should have memorized the six “strong” acids—those that can completely dissociate in water—memorizing these six means that anything else that is not one of these is a weak acid. They are HCl, HBr, HI, H2SO4, HNO3, HClO4. Therefore, (a) The CNO- ion is called the fulminate ion. It is highly unstable and explosive. Its corresponding acid is called fulminic acid—this follows our convention of “ate” polyatomic ions adding the “ic” ending to the name of the acid. In any case, it is a weak acid. (b) HBr (hydrobromic acid) is one of our strong acids, so for this problem, it is the exception and the correct answer. (c) HF (hydrofluoric acid), as stated above, is not one of our six strong acids and so is a weak acid. (d) HNO2 (nitrous acid), as stated above, is not one of our strong acids and so is a weak acid. (e) HCN (hydrocyanic acid), as stated above, is not one of our strong acids and so is a weak acid. Answer B (1 point/6) 7. Which of the following is not a strong base? a) Ca(OH)2 b) KOH c) LiOH d) Sr(OH)2 e) NH3 Strong bases will either (1) directly give up OH- to a solution when they dissociate, or (2) consist of a soluble metal oxide, which, when it dissociates, will form 2 OH- ions as the dissociated oxygen will pull a hydrogen ion away from a water molecule (thus creating two hydroxide ions). Weak bases are those substances that can remove a hydrogen ion from a water molecule leaving a single OH- behind, but they can only - accomplish this weakly. (a) Ca(OH)2 (calcium hydroxide) will give up OH ions directly to solution, and so is a strong base. (b) KOH (potassium hydroxide) will give up OH- ions directly to solution, and so is a strong base. (c) LiOH (lithium hydroxide) - will give up OH ions directly to solution, and so is a strong base. (d) Sr(OH)2 (strontium hydroxide) will give up OH- ions directly to solution, and so is a strong base. (e) NH3 can only weakly remove a hydrogen ion from a water molecule, and so is a weak acid. This is the exception in the list. Answer E (1 point/7) 8. Which of the following is paired incorrectly? a) H2SO4 – strong acid b) HNO3 – weak acid Copyright © Cengage Learning. All rights reserved. Chapter Error! Unknown document property name.: Error! Unknown document property name. 72 c) Ba(OH)2 – strong base d) HCl – strong acid e) NH3 – weak base You should have memorized the six “strong” acids—those that can completely dissociate in water—memorizing these six means that anything else that is not one of these is a weak acid. They are HCl, HBr, HI, H2SO4, HNO3, HClO4. Strong bases will either (1) directly give up OH- to a solution when they dissociate, or (2) consist of a soluble metal oxide, which, when it dissociates, will form 2 OH- ions as the dissociated oxygen will pull a hydrogen ion away from a water molecule (thus creating two hydroxide ions). Weak bases are those substances that can remove a hydrogen ion from a water molecule leaving a single OH- behind, but they can only accomplish this weakly. Therefore, (a) H2SO4 is a strong acid and so is paired correctly. (b) HNO3 is a - strong acid and so is not paired correctly. (c) Ba(OH)2 will give up OH ions directly to solution, and so is a strong base, and so, is paired correctly. (d) HCl is a strong acid and so is paired correctly. (e) NH3 can only weakly remove a hydrogen ion from a water molecule, and so is a weak acid. Answer B (1 point/8) 9. The man who discovered the essential nature of acids through solution conductivity studies is a) Priestly b) Boyle c) Einstein d) Mendeleev e) Arrhenius Arrhenius discovered that the essential nature of acids was in the dissociation of the acid molecule into a hydrogen ion (which we now know is “donated” to a water molecule to form the hydronium ion) and the anion corresponding to whatever the specific acid is. This dissociation was discovered in the larger context of discovering that when ionic substances in general dissociate completely, they easily conduct electricity. So, acids become one type of a larger class of compounds called electrolytes. Acids (or ionic substances) that completely dissociate in water are strong electrolytes.
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  • Barium Chloride, Dihydrate Safety Data Sheet According to Federal Register / Vol

    Barium Chloride, Dihydrate Safety Data Sheet According to Federal Register / Vol

    Barium Chloride, Dihydrate Safety Data Sheet according to Federal Register / Vol. 77, No. 58 / Monday, March 26, 2012 / Rules and Regulations Date of issue: 04/16/2014 Revision date: 03/13/2019 Supersedes: 10/28/2016 Version: 1.2 SECTION 1: Identification 1.1. Identification Product form : Substance Substance name : Barium Chloride, Dihydrate CAS-No. : 10326-27-9 Product code : LC11560 Formula : BaCl2.2H2O Synonyms : barium dichloride, dihydrate / muriate of barium, dihydrate 1.2. Recommended use and restrictions on use Use of the substance/mixture : Chemical intermediate Insecticide 1.3. Supplier LabChem, Inc. Jackson's Pointe Commerce Park Building 1000, 1010 Jackson's Pointe Court Zelienople, PA 16063 - USA T 412-826-5230 - F 724-473-0647 1.4. Emergency telephone number Emergency number : CHEMTREC: 1-800-424-9300 or +1-703-741-5970 SECTION 2: Hazard(s) identification 2.1. Classification of the substance or mixture GHS-US classification Acute toxicity (oral) H301 Toxic if swallowed Category 3 Hazardous to the aquatic H402 Harmful to aquatic life environment - Acute Hazard Category 3 Full text of H statements : see section 16 2.2. GHS Label elements, including precautionary statements GHS US labeling Hazard pictograms (GHS US) : GHS06 Signal word (GHS US) : Danger Hazard statements (GHS US) : H301 - Toxic if swallowed H402 - Harmful to aquatic life Precautionary statements (GHS US) : P264 - Wash exposed skin thoroughly after handling. P270 - Do not eat, drink or smoke when using this product. P273 - Avoid release to the environment. P301+P310 - IF SWALLOWED: Immediately call a POISON CENTER or doctor/physician. P330 - If swallowed, rinse mouth P405 - Store locked up.