General Chemistry - Standalone book (MindTap Course List)
General Chemistry - Standalone book (MindTap Course List)
11th Edition
ISBN: 9781305580343
Author: Steven D. Gammon, Ebbing, Darrell Ebbing, Steven D., Darrell; Gammon, Darrell Ebbing; Steven D. Gammon, Darrell D.; Gammon, Ebbing; Steven D. Gammon; Darrell
Publisher: Cengage Learning
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Textbook Question
Chapter 12, Problem 12.108QP

Analysis of a compound gave 39.50% C, 2.21% H, and 58.30% Cl. When 0.855 g of this solid was dissolved in 7.50 g of naphthalene, the solution had a freezing point of 78.0°C. The pure solvent freezes at 80.0°C; its molal freezing point constant is 6.8°C/m.

  1. a What is the molecular formula of the compound?
  2. b What is its molecular weight to the nearest 0.1 g?

(a)

Expert Solution
Check Mark
Interpretation Introduction

Interpretation:

A compound contains 39.50% Carbon , 2.21% Hydrogen and 58.30% Chlorine. 0.855 g of this substance is dissolved in 7.50 g of naphthalene and the solution has freezing point of 78°C. Molecular formula of the compound has to be determined.

Concept Introduction:

Depression in freezing point is the phenomenon of lowering of freezing point of a substance, which is considered as solvent, by adding a non-volatile solute.   It is expresses as –

ΔTf = Kf × m

Where,

ΔTf = depression in freezing pointKf  = cryoscopic constantm    = molality of the solute

Number of moles of a substance is related to molar mass of the substance as,

no.of moles massmolar mass

Answer to Problem 12.108QP

Molecular formula of the compound is determined as C12H8Cl6.

Explanation of Solution

Given that freezing point of the solution is 78°C. freezing point of pure naphthalene is 80°C . Kf for naphthalene is 6.8°C/m. rewriting the depression in freezing point equation, determine the molality of the solution.

m = ΔTfKf = [80°C78°C)]6.8°C/m = 0.294 m

Number of moles of the compound considering 1 kg of solvent,

moles = 0.294 mol1 kg of solvent×0.00750 kg = 2.21×103 mol

Molar mass of the compound is calculated as,

molar mass =  0.855 g2.21×103 mol = 387 g/mol

Number of moles of elements in 100 g of the compound are calculated as follows -

moles of C = 39.50 g C × 1 mol12.01 g C = 3.2889 molmoles of H = 2.21 g H × 1 mol1.008 g H = 2.192 molmoles of Cl = 58.30 g Cl × 1 mol16.00 g Cl = 1.6466 mol

From the above calculation we could deduce that mole ratio of the elements Carbon, Hydrogen and Chlorine is 2:1.33:1 .  Multiply this by three to ease the calculation.  Thus the mole ratio of the elements is 6:4:3 .  Hence the empirical formula of the compound could be C6H4Cl3.   Unit formula mass of this compound is approximately equal to 182.5 amu. Previously we have calculated the molar mass of the compound as 387 g/mol. this is approximately equal to twice the value of 74 amu. hence the molecular formula of the compound could be (C6H4Cl3)2 which is C12H8Cl6.

(b)

Expert Solution
Check Mark
Interpretation Introduction

Interpretation:

A compound contains 39.50% Carbon , 2.21% Hydrogen and 58.30% Chlorine. 0.855 g of this substance is dissolved in 7.50 g of naphthalene and the solution has freezing point of 78°C. Molar mass of the compound nearest to the tenth of a gram has to be determined.

Concept Introduction:

Depression in freezing point is the phenomenon of lowering of freezing point of a substance, which is considered as solvent, by adding a non-volatile solute.   It is expresses as –

ΔTf = Kf × m

Where,

ΔTf = depression in freezing pointKf  = cryoscopic constantm    = molality of the solute

Number of moles of a substance is related to molar mass of the substance as,

no.of moles massmolar mass

Answer to Problem 12.108QP

Molar mass of the compound nearest to tenth of a gram is calculated to be  364.9 g/mol.

Explanation of Solution

Molar mass of the compound nearest to tenth of a gram is calculated as,

12 C (12.01)+8 H (1.008)+6 Cl (16.00) = 364.884 g/mol = 364.9 g/mol

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Chapter 12 Solutions

General Chemistry - Standalone book (MindTap Course List)

Ch. 12.4 - Prob. 12.7ECh. 12.4 - A solution is 0.120 m methanol dissolved in...Ch. 12.4 - A solution is 0.250 mole fraction methanol, CH3OH,...Ch. 12.4 - Urea, (NH2)2CO, is used as a fertilizer (sec the...Ch. 12.4 - Prob. 12.11ECh. 12.5 - Naphthalene, C10H8, is used to make mothballs....Ch. 12.5 - Prob. 12.5CCCh. 12.6 - How many grams of ethylene glycol, CH2OHCH2OH,...Ch. 12.6 - A 0.930-g sample of ascorbic acid (vitamin C) was...Ch. 12.6 - A 0.205-g sample of white phosphorus was dissolved...Ch. 12.7 - Calculate the osmotic pressure at 20C of an...Ch. 12.7 - Prob. 12.6CCCh. 12.8 - Prob. 12.17ECh. 12.8 - Each of the following substances is dissolved in a...Ch. 12.9 - Prob. 12.18ECh. 12.9 - If electrodes that are connected to a direct...Ch. 12 - Prob. 12.1QPCh. 12 - Prob. 12.2QPCh. 12 - Explain in terms of intermolecular attractions why...Ch. 12 - Prob. 12.4QPCh. 12 - Using the concept of hydration, describe the...Ch. 12 - What is the usual solubility behavior of an ionic...Ch. 12 - Give one example of each: a salt whose heat of...Ch. 12 - What do you expect to happen to a concentration of...Ch. 12 - Prob. 12.9QPCh. 12 - Pressure has an effect on the solubility of oxygen...Ch. 12 - Prob. 12.11QPCh. 12 - When two beakers containing different...Ch. 12 - Prob. 12.13QPCh. 12 - Prob. 12.14QPCh. 12 - Prob. 12.15QPCh. 12 - Prob. 12.16QPCh. 12 - One can often see sunbeams passing through the...Ch. 12 - Prob. 12.18QPCh. 12 - Explain on the basis that like dissolves like why...Ch. 12 - Prob. 12.20QPCh. 12 - Calculate the number of moles of barium chloride...Ch. 12 - Prob. 12.22QPCh. 12 - If 291g of a compound is added to 1.02 kg of water...Ch. 12 - A 5.1-g sample of CaCl2 is dissolved in a beaker...Ch. 12 - Consider two hypothetical pure substances, AB(s)...Ch. 12 - Equal numbers of moles of two soluble, substances,...Ch. 12 - Even though the oxygen demands of trout and bass...Ch. 12 - You want to purchase a salt to melt snow and ice...Ch. 12 - Prob. 12.29QPCh. 12 - Prob. 12.30QPCh. 12 - Prob. 12.31QPCh. 12 - Consider the following dilute NaCl(aq) solutions....Ch. 12 - Prob. 12.33QPCh. 12 - Prob. 12.34QPCh. 12 - If l-mol samples of urea, a nonelectrolyte, sodium...Ch. 12 - Prob. 12.36QPCh. 12 - Prob. 12.37QPCh. 12 - Prob. 12.38QPCh. 12 - Prob. 12.39QPCh. 12 - Prob. 12.40QPCh. 12 - Arrange the following substances in order of...Ch. 12 - Indicate which of the following is more soluble in...Ch. 12 - Prob. 12.43QPCh. 12 - Which of the following ions would be expected to...Ch. 12 - Arrange the following alkaline-earth-metal iodates...Ch. 12 - Explain the trends in solubility (grams per 100 mL...Ch. 12 - The solubility of carbon dioxide in water is 0.161...Ch. 12 - Prob. 12.48QPCh. 12 - Prob. 12.49QPCh. 12 - Prob. 12.50QPCh. 12 - Prob. 12.51QPCh. 12 - Prob. 12.52QPCh. 12 - Vanillin, C2H2O3, occurs naturally in vanilla...Ch. 12 - Lauryl alcohol, C12H25OH, is prepared from coconut...Ch. 12 - Fructose, C6H12O6, is a sugar occurring in honey...Ch. 12 - Caffeine. C8H10N4O2, is a stimulant found in tea...Ch. 12 - A 100.0-g sample of a brand of rubbing alcohol...Ch. 12 - An automobile antifreeze solution contains 2.50 kg...Ch. 12 - Prob. 12.59QPCh. 12 - Prob. 12.60QPCh. 12 - Concentrated hydrochloric acid contains 1.00 mol...Ch. 12 - Concentrated aqueous ammonia contains 1.00 mol NH3...Ch. 12 - Prob. 12.63QPCh. 12 - Prob. 12.64QPCh. 12 - A solution of vinegar is 0.763 M acetic arid,...Ch. 12 - A beverage contains tartaric acid, H2C4H4O6, a...Ch. 12 - Calculate the vapor pressure at 35C of a solution...Ch. 12 - What is the vapor pressure at 23C of a solution of...Ch. 12 - What is the boiling point of a solution of 0.133 g...Ch. 12 - A solution was prepared by dissolving 0.800 g of...Ch. 12 - An aqueous solution of a molecular compound...Ch. 12 - Urea, (NH2)2CO, is dissolved in 250.0 g of water....Ch. 12 - Prob. 12.73QPCh. 12 - Prob. 12.74QPCh. 12 - Safrole is contained in oil of sassafras and was...Ch. 12 - Butylated hydroxytoluene (BHT) is used as an...Ch. 12 - Prob. 12.77QPCh. 12 - Prob. 12.78QPCh. 12 - What is the freezing point of 0.0075 m aqueous...Ch. 12 - What is the freezing point of 0.0088 m aqueous...Ch. 12 - Prob. 12.81QPCh. 12 - In a mountainous location, the boiling point of...Ch. 12 - Prob. 12.83QPCh. 12 - Prob. 12.84QPCh. 12 - Prob. 12.85QPCh. 12 - Prob. 12.86QPCh. 12 - A gaseous mixture consists of 87.0 mole percent N2...Ch. 12 - A natural gas mixture consists of 88.0 mole...Ch. 12 - Prob. 12.89QPCh. 12 - Prob. 12.90QPCh. 12 - A 55-g sample of a gaseous fuel mixture contains...Ch. 12 - Prob. 12.92QPCh. 12 - A liquid solution consists of 0.30 mole fraction...Ch. 12 - What is the total vapor pressure at 20C of a...Ch. 12 - A sample of potassium aluminum sulfate 12-hydrate....Ch. 12 - A sample of aluminum sulfate 18-hydrate,...Ch. 12 - Urea, (NH2)2CO, has been used to melt ice from...Ch. 12 - Calcium chloride, CaCl2, has been used to melt ice...Ch. 12 - Prob. 12.99QPCh. 12 - Prob. 12.100QPCh. 12 - Which aqueous solution has the lower freezing...Ch. 12 - Which aqueous solution has the lower boiling...Ch. 12 - Commercially, sulfuric acid is usually obtained as...Ch. 12 - Prob. 12.104QPCh. 12 - A compound of manganese, carbon, and oxygen...Ch. 12 - A compound of cobalt, carbon, and oxygen contains...Ch. 12 - The carbohydrate digitoxose contains 48.64% carbon...Ch. 12 - Analysis of a compound gave 39.50% C, 2.21% H, and...Ch. 12 - Fish blood has an osmotic pressure equal to that...Ch. 12 - Prob. 12.110QPCh. 12 - Prob. 12.111QPCh. 12 - Prob. 12.112QPCh. 12 - How are phospholipids similar in structure to a...Ch. 12 - Prob. 12.114QPCh. 12 - Two samples of sodium chloride solutions are...Ch. 12 - Prob. 12.116QPCh. 12 - You have an aqueous, dilute solution of a...Ch. 12 - Prob. 12.118QPCh. 12 - Prob. 12.119QPCh. 12 - Prob. 12.120QPCh. 12 - When 79.3 g of a particular compound is dissolved...Ch. 12 - What is the boiling point of a solution made by...Ch. 12 - Prob. 12.123QPCh. 12 - Prob. 12.124QPCh. 12 - Prob. 12.125QPCh. 12 - Prob. 12.126QPCh. 12 - Prob. 12.127QPCh. 12 - Prob. 12.128QPCh. 12 - An aqueous solution is 0.797 M magnesium chloride....Ch. 12 - A CaCl2 solution at 25C has an osmotic pressure of...Ch. 12 - Prob. 12.131QPCh. 12 - Prob. 12.132QPCh. 12 - The lattice enthalpy of sodium chloride, H for...Ch. 12 - Prob. 12.134QPCh. 12 - Prob. 12.135QPCh. 12 - Prob. 12.136QPCh. 12 - Prob. 12.137QPCh. 12 - An aqueous solution is 20.0% by mass of sodium...Ch. 12 - Prob. 12.139QPCh. 12 - The freezing point of 0.109 m aqueous formic acid...Ch. 12 - A compound of carbon, hydrogen, and oxygen was...Ch. 12 - A compound of carbon, hydrogen, and oxygen was...
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