Questions tagged [homework]

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Melting Points Because of Electronegitivity [on hold]

Why is sodium iodides melting point lower than calcium chloride?
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1answer
343 views

Lab test to compare the reactivity of liquid 1-heptene and liquid heptane

Describe how you would carry out a lab test to compare the reactivity of liquid 1-heptene and liquid heptane. State clearly what the possible results of the test are and what they would indicate. ...
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2answers
13k views

How does the polarity of the eluent and sample affect the Rf value in thin layer chromatography?

A three-component mixture (X, Y, Z) was separated using normal phase TLC. Three eluents of varying polarity were used. Select the TLC plate that was developed using the least polar eluent (click on ...
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1answer
734 views

Mg and Cu Reaction in HCl

When a solid piece of Mg is attached to a solid piece of Cu and is placed into HCl(aq), why does it appear that the Cu slowly starts to bubble?
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1answer
852 views

Osmotic pressure of a solution of a protein?

A small protein molecule, code-named "sloth", has a MM of $\mathrm{1.50 x 10^4}$ g/mol. What is the osmotic pressure exerted at $\mathrm{24.0^oC}$ by 25.0 mL of an aqueous solution that contains $\...
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2answers
770 views

Understanding how electrons are counted for lone pairs vs. bonds especially when understanding resonance?

This is taken from the book Organic Chemistry as a Second Language from page 35. In the following image: It is seen that when the electrons from the double bond are pushed into the lone pair ...
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1answer
5k views

Relationship between a temperature increase of an exothermic reaction, Keq, and kf (forward rate constant)

I'm currently stuck on #30 for Chemistry Olympiad 2015 local exam which reads as: For a reversible exothermic reaction, what is the effect of increasing temperature on the equilibrium constant (Keq) ...
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1answer
3k views

Calculating the pH of the endpoint in a titration of weak acid and strong base

Show that the pH at the endpoint in the titration of $\mathrm{0.100\ mol\ dm^{-3}}$ ethanoic acid with $\mathrm{0.100\ mol\ dm^{-3}}$ sodium hydroxide is 8.72. The dissociation constant Ka of ethanoic ...
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2answers
470 views

How to properly rearrange the first law of thermodynamics?

For class we have been asked to show how the First Law of thermodynamics. $$\mathrm dU = \mathrm dQ + \mathrm dW$$ can be shown to be $$\mathrm dQ = \frac{C_V}{R}V\,\mathrm dP + \frac{C_p}{R}P\,\...
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1answer
511 views

Simple Distillation of Unknowns

Can an identification experiment (using acetonitrile, isopropyl, and cyclohexane) using simple distillation and boiling point be improved by using a digital thermometer? Can simple distillation be ...
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1answer
358 views

Do cycloalkanes have open chain Alkene isomers?

I've been trying the get the number of isomers of bromocyclohexane and 1,2-dibromocyclohexane.I was taught that every cycloalkane should have an isomer that's an open chained alkene. I searched ...
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1answer
96 views

Nucleophilicity of alcoxy groups

I found a nucleophilicity order as $\ce{HO-} > \ce{CH3-O-} > \ce{(CH3)2CH-O-} > \ce{(CH3)3C-O-}$ The reason was given that bulky groups reduce nucleophilicity. But why? The order of the $+...
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2answers
251 views

Why do substances ionise in water to turn into charged species? Wouldn't they prefer to stay as uncharged molecules?

Wouldn't this be more stable if they stayed as neutral molecules? I've learnt that they will seek to reach the ratio of $[A]^a[B]^b/[C]^c$ that matches the $\ce{Ka}$ or $\ce{Kb}$ value. But I do ...
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1answer
2k views

Unit conversion of Molar Conductivity

I know this might be a silly question but I am confused with different answers of internet. My question is: Molar conductivity is given as: Molar conductivity = $k÷M$. SI unit of : k is S/m & ...
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1answer
7k views

Solubility order for alcohols [closed]

Order for solubility of isomeric alcohols in a book was given as: Primary alcohol >Secondary alcohol >Tertiary alcohol After this I found a question as : 1) Which is more soluble in water? (a) 3-...
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3answers
2k views

What is CuCl.CO.2H2O?

What is the chemical $\ce{CuCl.CO.2H2O}$, formed via the reaction of copper chloride and carbon monoxide? Does this compound have any use or appear in any noteworthy reaction?
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1answer
96 views

Is Nuclear Spin Isomer a kind of allotrope?

In my book there's a question: Does $\ce{H2}$ shows allotropy ? Enlist its allotropes and their application? I pondered over different way Hydrogen can be arranged(I don't know but I have weak ...
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2answers
5k views

How to calculate what temperature change in entropy for the reaction equal to the change in entropy for the surroundings given Enthalpy and entropy

A reaction has $\Delta H_{rxn} = -107$ kJ and $\Delta S_{rxn} = 285$ J/K. At what temperature is the change in entropy for the reaction equal to the change in entropy for the surroundings? My ...
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2answers
910 views

When pH increases, does the effect of increased [OH-] or reduced [H+] control precipitation of CaC2O4

The image below shows how oxalic acid dissociates and forms calcium oxalate ($\ce{CaC2O4}$ or $\ce{Ca(OOC-COO) as written below}$). When the pH increases, does this result in more or less $\ce{Ca(OOC-...
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1answer
2k views

Stability by using charge/radius rule

I found a question Which is more stable among the following? (a) $\ce{CaCO3}$ (b) $\ce{MgCO3}$ Answer : (a) Explanation was given as: "$\ce{Mg^2+}$ has smaller radius than $\ce{Ca^2+}$ and thus $...
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1answer
348 views

Acidity of primary and secondary amines

I was reading a book on organic chemistry by David Klein and I came across this question, but I wasn't able to understand why one amine is more acidic than the other.
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2answers
3k views

How to Prepare a Buffer Solution?

Problem I am given the task of preparing three buffer solutions at pH 10, 9.5, and 9.0. I have available concentrated ammonia and 3M hydrochloric acid. Attempt at Solving By adding HCl to a ...
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3answers
271 views

Is the amount of cubic inches in a cubic foot exact?

I know we are supposed to use SI units and I know they are defined very well. But does that mean that Imperial units of length/volume aren't exact? Don't they have infinite significant figures in ...
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1answer
581 views

Which is the base and acid in the reaction between thiosulfate and hydronium?

Is the following reaction an acid-base reaction: $$\ce{2 H3O+(aq) + S2O3^2-(aq) -> 3H2O(l) + SO2(g) + 1/8 S8(s)}$$ And if so, which is the acid and which is the base?
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2answers
2k views

What happens to acids/bases left out overnight?

I conducted a titration experiment a few days back and was unable to neutralize the solution in time, so I had to leave the solutions of HCl and NaOH out overnight in order to use them the next day. ...
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1answer
122 views

Why is brine solution more effective than granular salt in melting ice on a surface?

Why is brine solution consisting of a small fraction of salt plus water more effective in melting ice than just pure salt on an ice surface?
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1answer
5k views

How to calculate the van der Waals radius of ethane?

Calculate the van der Waals radius for ethane if $b = 0.0493\ \mathrm{dm^3\ mol^{-1}}$. $$b = 4 \times {4 \over 3}\pi \times r^3 \times N_\mathrm A$$ $$\implies r = \sqrt[3]{3b\over 16\pi N_\mathrm A}...
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1answer
2k views

Stoichiometry Chemistry Lab: Copper (II) Sulphate Pentahydrate and Iron Single Displacement Reaction?

In my grade 11 chemistry class, we performed a lab in which we added 1.00g of iron to 6.00g of copper (II) sulphate which was dissolved in water. Using stoichiometry, we predicted that if the iron was ...
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1answer
223 views

Predicting the product in a series of reactions

I am stuck in finding the final product $\ce{C}$ formed in the following series of reactions: $$\ce{Bu-C#CH ->[NaNH2] A ->[Ph-CHO][H2O] B ->[MnO2] C}$$ where $\ce{Bu}$ denotes the butyl ...
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2answers
3k views

Help with determining the rate constant of a reaction

The question asked was, The initial concentration of $\ce{N2O5}$ in the first order reaction $$\ce{N2O5 -> 2NO2 + 1/2O2}$$ is $1.24\cdot 10^{-2}~\mathrm{mol\,L^{-1}}$ at 318K. The ...
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2answers
5k views

Why and how carboxylate ion has greater stability than carboxylic acid?

I found it written in my textbook. I think it's a misprint, I can't think of any logic behind this statement. I've only learned that ion is less stable specie so carboxylate ion cannot be more stable ...
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1answer
1k views

How can I calculate the percentage of dissociated dinitrogen tetroxide?

When 36.8g $\ce{N2O4 (g)}$ is introduced into a 1.0-litre flask at 27 °C. The following equilibrium reaction occurs: $\ce{N2O4(g) <=> 2NO2(g)}$; $K_p = 0.1642~\mathrm{atm}$. We have to find the ...
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1answer
383 views

Stability order of octahydrobiphenylenes

I am facing trouble in the following question What is the stability order of the following compounds? In my view cis is less stable than trans. So if prior groups are on the same side of the ...
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2answers
219 views

A metal, M, forms two fluorides containing 40.43% F and 50.44% F by mass. Identify the metal

A metal, $\ce{M}$, forms two fluorides containing 40.43 % $\ce{F}$ and 50.44 % $\ce{F}$ by mass. Identify the metal. I get that you can find out how much of the metal reacts with 1 mole of fluorine ...
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1answer
101 views

Arranging different oxygen-containing organic compounds by decreasing acidity

I am facing difficulty in the following problem. Arrange the following compound in decreasing order of acidity. It is clear that conjugate base of (Q) is more stable.hence it is most acidic....
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2answers
493 views

When finding hybridisation of atoms, why are double bonds and triple bonds only considered once?

To figure out what hybridization an atom has is to just count the number of atoms bonded to it and the number of lone pairs. Double and triple bonds still count as being only bonded to one atom. (...
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2answers
464 views

How can 2-indanone be prepared?

How do I prepare 2-indanone? Would adding phosgene to ortho-xylene lead to the formation of 2-indanone?
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2answers
31k views

How to determine which aqueous solution has the largest freezing point depression

Question This is more of a conceptual question. Let's say that we are given different aqueous solutions and we are asked to choose the one with the highest freezing point depression, which do we ...
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2answers
647 views

How can I derive whether the methyl cation or anion is planar?

According to VSEPR theory, in which species do all the atoms lie in the same plane? $\ce{CH3+}$ $\ce{CH3-}$ (A) 1 only (B) 2 only (C) both 1 and 2 (D) neither 1 nor 2 My try: ...
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1answer
611 views

Finding the molarity of an acid in a titration

I was doing a question that asks the molarity of a 10 mL of tartaric acid that is titrated to phenolphthalein endpoint with 20 mL of 1.0 M NaOH. I worked it out by equating the molarity of the NaOH ...
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2answers
2k views

How to determine which of two similar compounds has the larger dipole moment?

I am solving some problems involving the order of dipole moments of some compounds. I could solve most of them but the following. The question is to find out which has greater dipole moment $\ce{...
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1answer
107 views

Arrow pushing: why does the O become positive when its lone pair becomes a double bond?

In the following image: The oxygen's top pair of electrons forms a double bond. But in a covalent bonds, aren't the electrons shared? So won't the oxygen still have these $2$ electrons (that it ...
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2answers
2k views

When is rotation around double bonds to form cis-trans isomers allowed?

The Rhodopsin molecules in the retain contain a derivative of vitamin A called cis-retinal (Figure 6). On exposure to light, cis-retinal becomes an isomer called trans-retinal (Textbook Question). ...
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1answer
6k views

Help balancing reaction between Iron (II) chloride and potassium phosphate

Very rusty with chemistry and looking to review some basics. Came across the following: Iron(II) chloride and potassium phosphate react. Write and balance the molecular, ionic, and net ionic ...
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1answer
72 views

Heat exchange between tin and ethanol

This is a pretty straightforward heat/energy exchange problem, but I can't figure the answer out. A constant-pressure calorimeter contains $250.0\ \mathrm{mL}$ of ethanol (density = $7.89\ \mathrm{...
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1answer
404 views

What are the reactions occurring during the titration of a carbon dioxide contaminated water sample with diluted sodium hydroxide solution?

During estimation of dissolved $\ce{CO2}$ in water, we took a water sample, added few drops of phenolphthalein and titrated it against dil $\ce{NaOH}$. Questions What are the reactions that happen: ...
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1answer
84 views

Fe/Ga cell has a negative potential?

In the following homework problem, the answer says: "$E ^{o}_{cell}$ is negative, which makes the $\ce{Fe}$ and $\ce{Ga}$ half-reactions non-spontaneous." But I found $E ^{o}_{cell}$ to be positive ...
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1answer
482 views

Bond length comparison between sulfur tetrafluoride and thionyl tetrafluoride

I'm comparing sulfur tetrafluoride and thionyl tetrafluoride. The lone pair has more s character compared to a double bond. Therefore, sulfur in $\ce{SF4}$ should have a greater s character compared ...
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1answer
373 views

Why does bromide not react with water when methyl ammonium bromide is dissolved in water?

In the following reaction, the salt $\ce{CH3NH3Br}$ is formed: $$\ce{CH3NH2 + HBr -> CH3NH3Br} $$ In water this dissociates completely into $\ce{CH3NH3+}$ and $\ce{Br-}$ In my chemistry book, it ...
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1answer
424 views

Help with finding intermediates in the synthesis of Ritalin

Here I have a Chemistry Olympiad question I'm doing that outlines the synthesis of Ritalin. So far I've worked out A, Anion B-, and compound C (You can see my workings, as I've scanned and attached ...