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Uncertainty in a Lab

Question 1. A student reported the mass of 10 glass beads as 2.507 "+ or -" 0.015g. What should the student report as the mass of one bead? Question 2. A student reported the density of ten glass ...
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15 views

Redox Half Reaction - Reduction

I can't seem to figure out this redox reaction. Is the charge on the Carbon in the $\ce{CO2}$ supposed to match the charge on the Carbon in the $\ce{CH3COO-}$? I am supposed to build a half ...
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1answer
18 views

How to find the molar mass of an unknown metal carbonate through a gas evolution reaction?

As part of a pre-lab exercise in Chemistry, we went through the necessary calculations to identify an unknown metal in a metal carbonate. The method was gas evolution by means of hydrochloric acid ...
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1answer
43 views

How to calculate the concentration of all relevant species in a buffer of a given pH?

You prepare $1.0~\mathrm{L}$ of a $0.25~\mathrm{M}$ acetic acid solution with a final $\ce{pH}$ of $6.0$. What are the molar concentrations of all relevant acetic acid species ($[\ce{HA}]$ and ...
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1answer
24 views

What type of reagent can convert nitrobenzene to N-phenylhydroxylamine? [on hold]

We are required to convert nitrobenzene to N-phenylhydroxylamine. Under what conditions and/or reagents can it be achieved? Please justify also the same.
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1answer
29 views

Calculating the pressure of an ideal gas that undergoes isothermal expansion

A 2.35 mole sample of an ideal gas, for which $C_{v,m}=3R/2$ initially at $27^{o}$C and $1750$ kPa, undergoes a two stage transformation. For each of the stages described in the following list, ...
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0answers
19 views

How to determine the mole ratio of a given compound? [on hold]

A solution of $\ce{CuCl2.2H2O}$, $0.70~\mathrm{g}$, in hot water, $14.0~\mathrm{mL}$, is added to a boiling solution of 2,2’-bipyridine, $\ce{bipy}$, $1.50~\mathrm{g}$ in $40~\mathrm{mL}$ of ...
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1answer
65 views

What is a strong base?

How come that some insoluble compounds in water, e.g. $\ce{Mg(OH)2}$, $\ce{Ca(OH)2}$, $\ce{Sr(OH)2}$ are considered strong bases? Are they even strong bases? How can I tell if a compound is a strong ...
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1answer
25 views

Why does a container in which a match burning cause suction?

As you see in picture a burning match in a container causes suction and this is a Traditional Therapeutic method to relive bone pain. What is the reason? I think it should be related to gas ...
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15 views

combustion energy question [on hold]

When $1~\mathrm{mol}$ of propan-1-ol was burned, the temperature of $6~\mathrm{kg}$ of water increased by $80^{\circ}~\mathrm{C}$. Using this information what is the energy released by the combustion ...
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1answer
48 views

A 250g sample of a white solid was known to be a mixture of KNO3, BaCl2 and NaCl. [on hold]

Continued: When a 100g sample of this mixture was dissolved in wated and allowed to react with excess H2SO4, 67.3g of a white precipitate was collected. When the remaining 150g of the mixture was ...
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1answer
30 views

Synthesis of 2-Phenyl-2-Butanol from Grignard Reagent

The question is this: 2-Phenyl-2-Butanol can be synthesized by three different combinations of a grignard reagent and a ketone. Show each combination. I can only think of one. Butanone with ...
3
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2answers
81 views

How might you use a precipitation reaction to prepare a solution of CaCO3? [on hold]

My question is how to write a balanced equation and the net ionic equation for the precipitation reaction. The question also says include state symbols in your equation. Unfortunately, I am not ...
2
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0answers
73 views

What is the total concentration (in mol dm-3) of ions in each of the following solutions, assuming complete dissociation

$\text{0.750mol}~ \text{dm}^{-3}$ Solution of $\ce{K2CO3}$ (I believe is $\text{2.25mol dm}^{-3}$) $\text{0.355mol dm}^{-3}$ solution of $\ce{AlCl3}$ (I believe is $\text{1.42mol dm}^{-3}$) Does ...
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2answers
30 views

Possible ? / catalyst [on hold]

A reaction in which all the reactant and product are in the gaseous phase, can a solution be used as a homogenous catalyst? yes or no If yes explain
3
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1answer
28 views

Analytical Chemistry predicting the order of elution of compounds in a reverse phase HPLC

Predict the order of elution for a mixture containing caffeine and benzoic acid, using a reverse phase HPLC. Explain your answer. My try Since benzoic acid is more acidic that caffeine, which means ...
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1answer
32 views

Vapor Pressures [on hold]

A solution containing hexane and pentane has a vapor pressure of 247 torr at room temperature. Pure pentane and hexane have vapor pressures of 425 torr and 151 torr respectively at room temperature. ...
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1answer
27 views

Reagent Concentration [on hold]

After mixing 10ml of $\ce{H2SO4}$ with 10ml of $\ce{KOH}$ we obtained 5 μmol of $\ce{K2SO4}$. What was the concentration of the initial $\ce{H2SO4}$ solution? How is this solved? Thanks.
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1answer
119 views

The Verb for Polymorphism

How can you elegantly describe that a polymorphic substance changes its structure? it polymorphs it morphs it undergoes polymorphic transition it experiences a morphic change
2
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1answer
33 views

Polyprotic bases and acids

I just have a question on how do you do the polyprotic bases. Question: show how oxalate ion can be a polyprotic base: My answer -> $$\ce{OOCCOO ^{2-}+ HOH \rightarrow HOOCCOO^{-} + OH ^{-}}$$ ...
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1answer
100 views

Electronegativity and HCl and HF molecules

In a book I am reading, it is said In the $\ce{HCl}$ molecule, the shared pair of electrons spend more time nearer the chlorine atom. In the $\ce{HF}$ molecule, the shared electrons spend more ...
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4answers
86 views

Could I get a hint on the structure of this molecule based on HNMR spectra?

Chemical formula is $\ce{C7H6O3}$. IR spectra has a peak at 3238, which I believe could be an alcohol, phenol, or carboxylic acid. There's an additional peak at 3015, which I believe is either an ...
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0answers
21 views

I need help with a Stoichiometric question [closed]

23.8ml of sulphuric acid is neutralised by 29.9 ml of 2.86 mol of sodium hydrogen carbonate solution, according to the equation: $$\ce{2NaHCO3 (aq) + H2SO4 (aq) -> Na2CO3 (aq) + CO2 (g) + H2O ...
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2answers
41 views

Are all strong acids the same strength?

Since the six strong acids dissociate completely into their ions, and the reaction goes to completion, does this mean that acids such as $\ce{HI}$ and $\ce{HCl}$ have the same acidic strength? I know ...
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1answer
58 views

Dissociation of different compounds?

What would be the dissociation of Hydrosulfuric acid in the presence of water? I was thinking that Hydrosulfuric acid or $\ce{H2S}_{(aq)}$ would form $\ce{2 H+}$ and Sulfur ions. With this logic, I ...
2
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1answer
33 views

How to calculate the heat capacity of a calorimeter?

I need to find the heat lost of an unknown metal dropped into a calorimeter with $70~\mathrm{g}$ $\ce{H2O}$. The initial temperature and final temperature of the $70~\mathrm{g}$ $\ce{H2O}$ and the ...
2
votes
1answer
39 views

Order of molecular mass of solvent; given boiling point [closed]

So I got this question in my tuition test and the solution is unclear. This question is troubling me a lot. $Question:$ given three solvents X, Y, Z. Order of boiling point of pure solvent ...
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0answers
245 views

Calculate the percent of the initial after blue colour appears [closed]

Assume you mixed $20.00~\mathrm{mL}$ of $0.040~\mathrm{M}$ $\ce{KI}$ with $20.00~\mathrm{mL}$ of $0.060~\mathrm{M}$ $\ce{(NH4)2S2O8}$, $10.00~\mathrm{mL}$ of $0.00070~\mathrm{M}$ $\ce{Na2S2O3}$, ...
2
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1answer
42 views

Why does one bicyclic diastereomer react faster than the other one?

I have a difficult question in my problem sheet that I cannot solve. I have been asked to explain the following observation: I have a number of issues with this: 1) The fast reaction must be a ...
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0answers
22 views

Suppose one does a minor in chemistry, at the university level. After completing, what should he/she know? [closed]

Suppose one would do a minor in chemistry. In Europe, that would be about $25$ ECTS or $25 * 27 = 675$ hours of work by minimum ($1$ ECTS is about $27$ hours of work). After completing, what should ...
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21 views

d=m/v question about boat sinking [closed]

A little aluminum boat (mass of 14.8 g) has a volume of 450.00 cm3. The boat is place in a small pool of water and carefully filled with paper clips. If each paper clip has a mass of 2.2 g, how many ...
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1answer
52 views

the strongest intermolecular forces between hydrogen bromide and potassium permanganate? [closed]

the strongest intermolecular forces between $\ce{HBr}$ and $\ce{KMnO4}$? Is $\ce{HBr}$ polar nonpolar or ionic? how about $\ce{KMnO4}$?
3
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1answer
54 views

Reversible thermodynamic machine

Assume two identical solid blocks of copper with molar heat capacity at constant volume $C_{V,m}=24.5 \text{ J$\cdot$K$^{-1}$mol$^{-1}$}$ . Assume the heat capacity to be constant in the ...
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0answers
20 views

Why is an electron removed from the 4s instead of the 3d orbital, when ionizing an element from d block? [closed]

Why does electron get removed from $4s$ instead of $3d$ when ionizing an element from $d$ block? Answer is required in terms of effective nuclear charge
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1answer
35 views

Electron Pair Geometry in Ibuprofen (Electron Pair Geometry in Organic Compounds)

I am trying to determine the electron pair geometry (and molecular geometry) of some atoms in ibuprofen. The first one I am trying to do is the double bonded oxygen. Ibuprofen is pictured below: I ...
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1answer
34 views

How is the Rate Law of a reaction measured?

What is Rate Law of the reaction below?$$\ce{4 HBr + O2 -> 2 H2O + 2 Br2}$$ How do we approach finding the rate law of reaction? Can this be found out only through experiments?
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0answers
19 views

So of the different characteristics of a XRD plot, wich is most appropiate to identify and suggested one phase among others?

This is the XRD Powder plot of a sample prepared with {La, Ti, K and O}. Thanks a lot for your suggestions. So of the different characteristics of a XRD plot, which is most appropriate and suggested ...
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2answers
39 views

Thermogravimetric Analysis of hydrated compounds

I have been given this thermogravimetric analysis of my compound $\ce{NiBr2.$x$\,H2O}$ and I need to work out the number of moles of water in the complex. Also why are there two steps in the data?
2
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1answer
40 views

How to determine number of alpha hydrogens in a cyclic compound?

How do we determine the number of alpha hydrogens in a compound? Where should we start the naming from? For example, In both these structures, I need to determine their stabilities based on their ...
3
votes
1answer
45 views

What is the effect of Oxygen on soap foam?

I've been wondering the effect of $\ce{O2}$ on soap foam in a closed, test room. The room contains a candle and soap foam. That is to say: if the room has lower and decreasing $\ce{O2}$ in its air, ...
2
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0answers
38 views

Woodward Hoffmann rules for electrocyclic reactions

For the thermal electrocyclic cleavage of cyclobutene to 1,3-butadiene, what is the correct assignment of the orbital components ? My attempt: I know this reaction is allowed (4n thermal ...
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1answer
32 views

Impurity of a salt in this reaction [closed]

$49~g$ of 1.5% $\ce{NaCl}$ (39.34%$\ce{Na}$ ;60.66% $\ce{Cl}$) reacts with an excess of $\ce{AgNO3}$. $1.6g$ of depostion is formed. What percent of impurity does the salt contain? (It's known that ...
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2answers
38 views

How to calculate the vapor pressure of water?

$48~\mathrm{l}$ of dry $\ce{N2}$ passes through $36~\mathrm{g}$ $\ce{H2O}$ at $300~\mathrm{K}$, and this results in a water loss of $1.20~\mathrm{g}$. The vapor pressure of water is? The solution ...
2
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1answer
39 views

What gas arises from the reaction between 2-methyl-2-bromopropane and hydroxide (Sn1-reaction)?

I know the majority of yield will be in the form of 2-methyl-2-propanol and a Bromide anion, but what sideproduct will exist that is gaseous? Thanks!
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2answers
80 views

How to determine the empirical formula for terephthalic acid from its combustion products?

Terephthalic acid is an important chemical used in the manufacture of polyesters and plasticisers. It contains only $\ce{C}$, $\ce{H}$, and $\ce{O}$. In one experiment, $0.4953~\mathrm{g}$ of the ...
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1answer
38 views

ph & pOH - Autoionization of Water

So I was learning about pH and pOH and it made sense. I looked at strong, weak acids & bases and learned that they dissociate completely in water. So then I moved on to water and learned about the ...
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2answers
37 views

How does this method of calculating the water equivalent of a calorimeter work?

I am doing a AP Chemistry lab in which we determine the heat capacity of a calorimeter (a concept that seems like it should depend on a lot more than just the calorimeter.) We have to calorimeters ...
2
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1answer
60 views

Volume of 1 Mole of Liquid Water

I am doing some rough calculations to test my understanding of elementary chemistry. In what follows, I calculate the volume of one mole of liquid water at about $4~^\circ\mathrm{C}$ and ...
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3answers
83 views

In order to be a gas does the pressure exerted by the gas has to be more than the atmospheric pressure?

In order to be a gas does the pressure exerted by the gas has to be more than the atmospheric pressure? Really simple, I think yes to this question but teacher says no. So what is your view into this? ...
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3answers
68 views

Beta Decay - Doesn't Add Up [duplicate]

The definition of Beta Decays is as follows Electron comes out. Example as follows: $$\ce{^131_53I -> ^131_54Xe + e^-}$$ So Iodine forms Xe and releases one electron with a -1 charge only and ...