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The mole is a standard amount of a substance A mole of a substance is a number of units (particles, atoms, molecules, ions, peas, hard candies, people, universes) equal to the number of atoms of carbon-12 in one gram of carbon-12, or an Avogadro's number of stuff. The mole allows us to relate real-...

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Effect of redefining Avogadro's constant and kilogram on molar mass

Avogadro's constant $N_A$ is defined as the number of constituent particles (usually atoms or molecules) contained in the amount of substance given by one mole. The value of Avogadro's constant $N_A$ ...
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21 views

How many liter of air are required?

I have the following question : Producer gas has the following composition in precent of volume : $8.0$%$CO_2$, $23.2$%$CO$, $17.7$%$H_2$, $1.1$%$CH_4$, $50$%$N_2$ How many liters of air (air ...
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1answer
54 views

I have a question involving a mole calculation which I was able to answer but took me a whole page. Whats the most efficient way of answering it? [closed]

A 10.00g, mixture of potassium carbonate and potassium hydrogen carbonate is heated to constant mass. The final mass was found to be 8.90g. calculate the % composition of the original mixture. My ...
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0answers
12 views

Finding molar fractions of components given density of total gas at stp

How can we find the molar fractions of n2 and o2 given that the whole gas has a density of 1.4 g/l at stp? I have seen solutions of this problem that first calculate the mass per volume of the ...
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3answers
39 views

Question about the mole [duplicate]

Why is it to get from x amu---->xgram you need a mole of the substance. I mean I underdstand this to be the case for Hydrogen. Why does a mole of a substance CONVERT the substances amu into grams?
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1answer
49 views

How to determine the volume of water necessary to produce a solution with 4.9 g/l sulfuric acid?

The molar mass of sulfuric acid is $M(\ce{H2SO4}) = \pu{98.1 g/mol}$. We have $\pu{100 mL}$ of a $0.1$ molar solution of sulfuric acid. What volume $V$ in $\mathrm{mL}$ of water, $\ce{H2O}$, do we ...
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1answer
16 views

Molarity of a substance in a solution when more fraction is given

Mole fraction of ethanol in a solution with water is $0.040$. What will be the molarity of ethanol in water? Density of water can be assumed to be $1\ \mathrm{g/mL}$. This is how I tackled the ...
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1answer
37 views

How are the molar mass and molecular mass of any compound numerically the same?

This observation is really annoying me, and the internet isn't providing me with any solid answers. Either their definitions of molar mass completely differ, or they don't stick to their own ...
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2answers
70 views

Does a stoichiometric coefficient represent molecules or moles of a substance?

I understand that the one mole of atoms is equal to $6.02\times10^{23}$ atoms. However, when I used various resources to learn about stoichiometry, they showed me a balanced equation: $$\ce{2H2O->...
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1answer
79 views

Is it possible for me to derive Avogadro's number?

To my understanding the mole is the unit used to translate between mass on the atomic level and mass in the macro level, defined as the number of atoms in $12$ grams of Carbon-$12$, which apparently ...
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1answer
67 views

How did early chemists measure mass of atoms?

Here a book says that Berzelius measured atomic masses using a simple lab and his measurements was so close to modern results. Can someone explain how a person living in 19th century was able to ...
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1answer
39 views

Is there a formula for density of any gaseous substance just based on its molar mass?

$\pu{112 ml}$ of hydrogen combines with $\pu{56 mL}$ of oxygen to form water. When $\pu{224 mL}$ of hydrogen is passed over heated cupric oxide, the cupric oxide loses $\pu{0.160 g}$ of its weight. ...
3
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0answers
41 views

Calculating amino acid mol/mol ratios

I am trying to understand how the authors calculated the TRP/LNAA (mol/mol) ratios in Table 1 in this paper. For example, when I calculate the TRP/LNAA (mol/mol) ratio for HPROT, I get 0.14 instead ...
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1answer
48 views

How to find the percentage composition of halogen using Carius method?

In the formula: $$\text{Percentage}=\frac{\text{atomic mass of halogen}}{\text{molecular mass of Agx}}\frac{\text{mass of AgX}}{\text{mass of compound}}\cdot100$$ here mass of compound is the mass ...
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2answers
85 views

Volume of composition of air

My teacher stated: At standard conditions, 1 liter of air at 21% oxygen possesses $\pu{0.21 L}$ of oxygen. Since at STP, 1 mole of gas occupies $\pu{22.4 L}$, simply divide $0.21/22.4$, to arrive ...
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1answer
23 views

Find volume of sample such that it contains 100ng of DNA

Im struggling with the maths of concentrationsand volumes and things..Ill give the question, then my thoughts on it: A DNA trimer strand, ab, has moleuclar weight of $9309ng/\mu mol$. I#m designing a ...
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0answers
96 views

Is Avogadro's number an integer? [duplicate]

I have heard that Avogadro's number, $N_\mathrm A=6.022 \times 10^{23}$, is the number of atoms contained in $12$ grams of $\ce{^{12}C}$. I think it should be an integer, but I couldn't find the exact ...
3
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1answer
144 views

Percentage purity of Ba(MnO4)2 sample that completely reacts with given H2O2?

$\pu{40 g}$ $\ce{Ba(MnO4)2}$ (mol. wt. = 375) sample containing some inert impurities in acidic medium is completely reacted with $\pu{125 mL}$ of $\pu{3 M}$ $\ce{H2O2}$. What is the percentage purity ...
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1answer
228 views

Why does 1 mol. of any gas at STP occupy only 22.4L Volume when it should occupy the volume of entire container in which it is kept? [duplicate]

Let us say we have a container of 100L capacity and a gas inside it is kept at STP. According to the law the gas should occupy only 22.4L of volume but shouldn't the gas occupy the entire volume of ...
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1answer
85 views

Calculating the Radius of a Molecule

Assuming the molecule is a sphere, would the radius of amylopectin be $9.17*10^{-22}~cm^3$? I arrived at this answer by deriving the molar volume by dividing the molar mass ($828.72~g/mol$) of ...
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0answers
33 views

Calculation of Molar Mass

What is the molar mass of whey protein isolate? I already know that whey protein consists 70% of β-lactoglobulin (18.3 kDa) and (30%) of α-lactalbumin (14.2 kDa), however, as their molecular weights ...
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1answer
603 views

What's the relation between molarity and molality?

I am trying to derive the relation between the molarity and molality of a solution Mole concept $\displaystyle n = \frac{M'}{M''}$ Here, ($n$) stands for number of moles $\ce{(M^{'})}$ stands for ...
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1answer
780 views

Calculating the pH upon titrating barium hydroxide and hydrochloric acid

Question: Calculate the pH produced from mixing $\pu{25.0 mL}$ of $\pu{0.420 M} $ $\ce{Ba(OH)_2}$ with $\pu{125 mL}$ of $\pu{0.120 M}$ $\ce{ HCl}$. Attempt: I'm learning about acids and bases ...
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0answers
36 views

Why isn't the sum of the volume of the reactants the same volume as product?

Imagine that we needed to work out the volume of $\ce{SO2 and O2 that would produce 0.180dm^3 of SO3}$ $$\ce{2SO2 + O2->2SO3}$$ By using Volume = Moles$\mathrm{~ \times 24 ~dm^3}$ We can ...
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1answer
70 views

What to say 'one mole of C atoms or one mole of C molecules?

What to say 'one mole of C atoms or one mole of C molecules in CO? Please point out if I am wrong here As we know, one molecule of CO = one mole of CO molecules = 6.223 X 10^23 number of CO molecules ...
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1answer
58 views

Does mass equal to moles times molar mass take into account coefficients?

I have an equation $$\ce{ 2NaN3 -> 2Na + 3N2}$$ I've calculated there are $\pu{4.4 moles}$ of $\ce{N2}$ (using the data given in the question). I then did $\large{\frac{4.4}{3 \cdot 2}}$ to get ...
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1answer
77 views

Calculate the formula, and moles

If $\ce{1.84\times10^{-4}}$ moles of element A was completely reacted with element B to create $\ce{1.231\times 10^19}$ molecules of $\ce{(A3B2)_x}$ a hypothetical compound, what is the value of x? I ...
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0answers
33 views

Standardising sodium hydroxide

Using an average titration volume of $\pu{26.8mL}$ of sodium hydroxide, calculate the concentration of the $\ce{NaOH}$ solution. ($\ce{NaOH}$ & $\ce{KH(C8H4O4)}$ molar ratio = $1:1$). Given that ...
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1answer
205 views

Acetic acid in vinegar [closed]

How do I calculate the number of moles of acetic acid present in 25 mL of a 10% vinegar solution?
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2answers
4k views

Avogadro's Number: 6.023 x 10^23 or 6.022 x 10^23? [duplicate]

I was taught that Avogadro's number was $6.023 \cdot 10^{23}$. Now, the accepted value is allegedly $6.022 \cdot 10^{23}$. Has there been a change? If so, when and why? There are still some sites that ...
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1answer
167 views

How to define equivalents here

$3g$ of activated charcial was added to $50 ml$ of acetic acid solution ($0.06N$) and filtred after an hour and it was found to be $0.042 N$ .The amount of acetic acid adsorbed (per gram of charcoal) ...
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1answer
44 views

Where am I wrong in my calculations? [closed]

I am revisiting the concept of mole and I decided to figure out random values (for instance: mass of 1 molecule of water) to see how much I understand the concept of moles and how it relates to amu. ...
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1answer
75 views

Mass of iron from the reduction of iron(III) oxide [closed]

Given the equation $$\ce{Fe2O3 + 3H2 -> 2Fe + 3H2O},$$ determine how many grams of $\ce{Fe}$ can be produced from $\pu{16.5 g}$ of $\ce{Fe2O3}$. I've already determined the masses of each ...
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93 views

Validity of Law of Equivalence

Is law of equivalence valid for partial displacement reactions? 【I found this in my textbooks: According to the law of equivalence, whenever two substances react, the equivalents of one will be equal ...
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2answers
100 views

Neutralization of alkali solution by a mix of strong acids

$\pu{0.1 M}$ $\ce{HCl}$ and $\pu{0.2 M}$ $\ce{H2SO4}$ solutions are mixed in equal volume. This solution is diluted to double the volume. Find the volume of $\pu{0.1 M}$ $\ce{NaOH}$ which can be ...
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1answer
155 views

Propane-water molar ratio [closed]

Propane gas, $\ce{C3H8}$, burns in oxygen to produce carbon dioxide and water vapour as follows: $$\ce{C3H8 (g) + 5O2 (g) = 3 CO2(g) + 4 H2O (g) + \pu{2200 kJ}}$$ If $\pu{1.5 mol}$ of ...
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1answer
202 views

Mass of chromium in ammonium dichromate

What mass of chromium is in $\pu{100 mL}$ of $\pu{0.0400 mol/L}$ $\ce{(NH4)2Cr2O7}$? The specific concept is how to find the mass of a certain ion/element in a substance, given the concentration. I ...
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2answers
123 views

A mole of atoms is the number of atoms whose total weight equals the atomic weight?

My textbook says, a mole of atoms is the number of atoms whose total weight = the atomic weight. There's something in the definition that's confusing me. Now what is confusing me is: Atomic weight =...
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1answer
599 views

Confusion in n-factor calculation

How do we calculate the equivalent weight of a compound, in a case where certain fraction of an element of the compound is getting reduced, while the other fraction is unaffected (no change in ...
1
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1answer
134 views

Isotopic mass to density

I want to figure out/calculate the density ($\pu{g/cm3}$) of the various isotopes, here $\ce{^109Ag}$. I know it's isotopic mass is $\approx109$ and calculated the number of particles/gram. But I ...
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1answer
52 views

How do I find the number of grams of the product when given reactants? [closed]

I have the following chemical equation $$\ce{H + O2 -> H2O}$$ which balances out to $$\ce{4H + O2 -> 2H2O}$$ How would I find out how many grams of $\ce{H2O}$ and $\ce{H}$ I have, if I ...
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1answer
93 views

Amount of substance expressed in yoctomole units

I stumbled upon a couple of papers where amounts were expressed in yoctomoles ([ymol], $\pu{10^{-24} mol}$) and I find it somewhat bothersome as 1 ymol would correspond to about 60% of atom/molecule/...
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0answers
56 views

Problem regarding failure of equivalence concept

Chile salt peter, a source of $\ce{NaNO3}$ also contains $\ce{NaIO3}$. The $\ce{NaIO3}$ can be used as a source of iodine, produced in the following reactions. \begin{align} \ce{IO3- + 3 HSO3- &...
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1answer
188 views

Find the Relative Error in the Mass of the Product

I have the following question, A student was given the assignment of $4.00$ $\pu{mL}$ of $0.50$ $\pu{M}$ $\ce{KI}$ with $16.00$ $\pu{mL}$ of $0.50$ $\pu{M}$ $\ce{Pb(NO3)2}$ in a stoichiometry ...
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1answer
171 views

Moles and chemical equations [closed]

Sulfur reacts with oxygen according to the following equation: 2S + 3O2 -----> 2SO3 If 4 moles of sulphur reacts with 9.5 moles of oxygen, how many moles of oxygen would remain after the reaction?
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1answer
852 views

What is the analogue of “molecule” for ionic compounds?

In a system, if we have $\pu{18 g}$ of $\ce{H2O}$ ($M_\mathrm r = 18$), we can say we have a mole of water molecules or $6 \times 10^{23}$ molecules. But in another system, if we have $\pu{342 g}$ of $...
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1answer
2k views

How many ions in 1.00 mol of NaCl [closed]

it's my first week of IB chem and I'm already confused. We learned how to find the number of atoms, but not specifically ions... is it the same? Similar? HELP
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2answers
8k views

Calculate the number of atoms of oxygen present in 1.3 mol of sulfuric acid

Calculate the number of atoms of oxygen present in $\pu{1.3 mol}$ of $\ce{H_2SO_4}$ 1 mol has $6.02\times 10^{23}$ atoms So $\pu{1.3 mol}$ must have $1.3 \times 6.02 \times 10^{23} = 7.826 \times 10^...
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1answer
55 views

Derivation of formula used in calculating molecular mass from a mixture

In a solution to a problem, to calculate Molecular mass of unknown gas from a mixture containing $\ce{O2}$ in $80~\%$, the author used the formula : $\frac{1}{\sqrt{M_\text{mix}}}=\frac{X_{\ce{O2}}}...
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1answer
3k views

Titration with Ca(OH)2

In the laboratory, $20.0$ milliliters of an aqueous solution of calcium hydroxide, $\ce{Ca(OH)2}$, was used in a titration. A drop of phenolphthalein was added to it to indicate the end point. The ...