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Questions tagged [mole]

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-word measurements to atomic scale phenomena.

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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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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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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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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 ...
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Graham's law of diffusion

The rates of diffusion of two gases $\ce{A}$ and $\ce{B}$ are in the ratio $1:4$. If the ratio of their masses present in the mixture is $2:3$, the ratio of their mole fraction is? My tries: $\frac{...
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Determining the purity of commercial NaCl

I am trying to figure out how to determine the percentage of NaCl in salt. My purpose is to be able to test the purity of salt that I received before washing so that I can determine the quality of the ...
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if you have 2.5 * 10^21 atoms of magnesium how many moles do you have? [closed]

If you have $\pu{2.5 * 10^21}$ atoms of magnesium, how many moles do you have?
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805 views

Proving 1 = 2 by POAC( Principle of Atom Conservation )

I have been told that applying POAC in any equation means conserving the number of moles of an element in both reactant and product . For example : $$\ce{H2 + O2 -> H2O}$$ Here when we apply ...
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426 views

How to calculate the mass of air that fits into a balloon of a certain size?

A hot air balloon has a $\pu{500 m^3}$ volume. How much mass of normal air fits into the balloon, if the relative molar mass is $\pu{28.8 g/mol}$? I am not sure if I should simply use the $PV=nRT$ ...
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How to calculate the charge on 1 gram ions Aluminum cation?

I want to find out the charge on 1 gram ions of $\ce{Al^3+}$ ions. I tried out by finding no. of moles as $ \frac{1}{27} $ , then no. of ions will be $ \frac{1}{27} × N_A $ , then total charge will ...
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How to calculate average volume of a molecule? [closed]

The molecular weight of glucose-1-phosphate is $\pu{260 g/mol}$ and its density is $\pu{1.5 g/mL}$. What is the average volume occupied by 1 molecule of this compound?
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Finding the volume of the mass percent

I have been trying to understand this question, but no result. It reads: Find the volume occupied by $\ce{H2SO4}$ in a $\pu{200 mL}$ solution with $\pu{0.5 mol/L}$ of 98% mass of $\ce{H2SO4}$. ...
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Finding the molar concentration of reactant used

We were given this problem at my university, and I can't seem to figure out how it was solved. The question says we have $\ce{NaHCO3}$ and 100 ml of $\ce{HCl}$ react and one of their products is $\ce{...
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Is “amount of substance” the same thing as “number of moles”?

Background: Amount of substance is a fundamental physical quantity which has mole (mol) as it's SI unit. Therefore all expressions for amount of substance should have the unit mole on simplification. ...
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Can I add the molarities of multiple solutes together?

If I am calculating the molarity of a solution in which more than one solute is dissolved, can I add the total number of moles of all the solutes together and divide it by the total volume of solvent ...
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How to find mole fraction of solvent and solute in a vapor pressure lowering problem?

At $25$ degrees celsius, the vapor pressure of pure benzene ($\ce{ C6H6}$) is $93.9$ torr. When a non-volatile solute is dissolved in benzene, the vapor pressure of benzene is lowered to $91.5$ torr. ...
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Alternative definition of the mole? [duplicate]

1 amu (atomic mass unit) is defined as the one twelfth of the mass of a carbon-12 atom. The mole is defined as the number of carbon-12 atom in 12 g of carbon-12. In other words, $$\require{cancel} 1 ...
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Calculating amount of alkali additions to get desired pH in (hard) cider

This is linked to my question over on the HomeBrew SE site: https://homebrew.stackexchange.com/questions/18837/reduce-acidity-of-hard-cider I haven't done chemistry since I was 17/18 but I remember ...
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What is the standard molar weight of Carbon, and why?

The mole is defined as the amount of a chemical substance which contains as many representative particles, e.g., atoms, molecules, ions, electrons, or photons, as there are atoms in 12 grams of carbon-...
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How to calculate the number of atoms of each element in Mg(NO3)2? [closed]

I'm working on chemistry and I'm not quite sure how to solve this question? I haven't worked with moles before and whenever I try to figure out how to do these types of question I only end up ...
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2answers
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How to choose the correct name for calcium sulfate based on a calculations of the crystallisation water included?

I have a test review question which i really need help on. It states : A student heated a sample of the hydrate $\ce{CaSO4 * xH2O}$ in an evaporating dish over a bunsen burner to remove all the ...
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Atomic mass unit based on other atoms

Question: Which one is larger: an atomic mass unit based on the current standard or one based on the mass of a Be-9 atom? My attempt: Current standard is $1/12$th the mass of a C-12 atom. New ...
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Why is the relative atomic mass numerically equal to the gram atomic mass of the Atom? [duplicate]

Why is it that the relative atomic mass of an atom is numerically equal to gram atomic mass? For example,Relative Atomic Mass of Oxygen= 16 u So,Gram atomic mass of Oxygen=16 g.
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1 mole of substance is equal to atomic/molecular mass in grams?

I have been reading the answer of this question here- Why is weight of 1 mole of substance equal to atomic/molecular mass in grams I feel that the answer writer was wrong to say that -"the ratio of g/...
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finding molar mass of a molecule [closed]

Why is the molar mass of a molecule defined as the the sum of molar mass of all the atoms present in the molecule? For example, suppose we have to calculate the molar mass of $\ce{H_2O} $ molecule. ...
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1answer
240 views

units of mole formula [closed]

I am a high school student.I am currently studying "moles" chapter in my textbook.I think my book is misleading me in regards with units of a formula. The formula is, NO.of moles= (Given mass of an ...
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Why is the mass of 1 mole of an atom/molecule equal to its gram atomic/molecular mass?(proof) [duplicate]

Why do we take the mass of 1 mole of an atom to be equal to its gram atomic mass and the mass of 1 molecule to be equal to its gram molecular mass? I want a mathematical rigorous proof. There are ...
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Equivalent weight of calcium phosphate

In a reaction, calcium phosphate is producing calcium hydrogen phosphate. Then we have to find the equivalent weight of calcium phosphate in this process. I tried as: Oxidation number of calcium ...
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1answer
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Stoichiometry and POAC Contradiction

Lets say we have the reaction $$\ce{H2 + O2 -> H2O}$$ And we are given 10 moles of $\ce{O2}$ and are asked that How many moles of hydrogen gas do we need to complete the reaction ? ...
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What does mol L−1 mean? [closed]

I am researching how to Determination of Vitamin C Concentration by Titration for my science fair project and it says Titrate the sample with $0.005~\mathrm{mol~L^{−1}}$ iodine solution. The ...
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What is a mole?

Is my understanding of the concept of a mole correct? The mole is a simply a number ($6.023 \times 10^{23}$). It's just like what a dozen would be like for eggs, except that the mole applies to atoms ...
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Why does Avogadro's number have the value it has? [duplicate]

As I was learning about Avogadro's number and I was wondering why is Avogadro's number equal to $6.02214\cdot 10^{23}$? I mean, how did chemists come up with this particular number?
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How to correctly write “7 apples” according to the international system of units (SI)

According to international system of units (SI), we can write "7 kg of apples" to refer to the mass of these apples. However, if we want refer to the amount of apples, that is, the number of ...
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Effects of Changing Avogadro's Constant

The Avogadro project suggests that we redefine the Avogadro constant to be equal to our best known estimate, $N_\mathrm{A} = 6.02214179 \times 10^{23}$, and redefine the kilogram based on the Avogadro ...
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What exactly is a mole?

Upon coming back to University I've started studying basic chemistry again. I've always had trouble with the concept of "moles". According to my study book, 1 mole of any element or compound is ...
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Why is molar mass the same as atomic mass? [duplicate]

I am completely confused about why molar mass is the same as atomic mass. Could someone help explain why, thoroughly, but in simplified terms?
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1answer
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Avogadro's number and percent error help?

Calculate the percent error in Avogadro’s number calculated by using the following experimental data. Pipette calibrated as 30 drops/mL Diameter of the watch glass: $15.5\ \mathrm{cm}$ Number of ...
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Why does a certain number of moles of gas occupy a set volume?

In class, I was taught that 1 mole of an ideal gas occupies a set volume eg 22.4 L at STP. Why does the gas only occupy a certain volume and not just keep expanding forever, having limitless volume? ...
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Pepto-bismol molar bismuth concentration

I want to measure the Bismuth molar concentration in the OTC drug "pepto bismol". 525 mg bismuth subsalicylate (C7H6BiO4) / 30 mL (17.5 mg/mL) molecular weight 363.10054 g/mol If I convert to mM (17....
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To find the value of x in a metal chloride MClx [closed]

A solution containing 0.1 mol of a metal chloride MClx requires 500 ml of 0.8 M AgNO3 solution for complete precipitation. The value of x is: (a) 1 (b) 2 (c) 4 (d) 3 Please answer with an ...
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How to calculate the number of atoms of each element in a urea?

I have a stoichiometry question which I answered incorrectly and I am not sure where I went wrong. The question is as follows: Urea, $\ce{(NH2)2CO}$, is used for fertilizer and many other things. ...
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2answers
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How to calculate the amount of substances product produces from the masses and amounts of starting materials?

Calculate the amount of carbon dioxide formed when we burn 1 mole of carbon in the presence of 16 g of dioxygen. $$\ce{C + O2 -> CO2}$$ 1 mole of carbon means 12 g. Therefore amount of ...
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How does 1 mole of a compound = the molecular weight of the compound?

I am reviewing moles, and came across this sentence in my book: One mole of a compound has a mass in grams equal the molecular weight of the compound expressed in amu and contains $6.022\times10^{...
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How to make by dilution a certain ion concentration

The question I'm trying to answer is this: What volume of $0.25\ \mathrm{mol/l}$ calcium nitrate is required to make by dilution with water $500\ \mathrm{cm^3}$ of a solution with a nitrate ion ...
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How is H2 2 moles [duplicate]

I saw a question that asked which expression can be used to designate 2 moles of atoms. The choices were H2 C02 2N20 2NaCl H2SO4 The answer is H2 but I was confused because I thought H2 is only 1 ...
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Does 12 amu really equal the mass of one carbon-12 atom? [duplicate]

As I was studying chemistry, I encountered atomic mass units (amu) and based on some calculations, I realized that some numbers don't work out. Apparently, 12 amu is the mass of a single carbon-12 ...
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1answer
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How many moles of sodium are there in 10mls of 30% sodium chloride?

How many moles of sodium are there in 10mls of 30% sodium chloride? 30% of 10mls is 3g NaCL. There is 3000mg of NaCl and would that be divided by the molecular weight of NaCl or of just Na? I ...
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Why are osmoles not considered SI units?

The Wikipedia article for osmoles is pretty clear on what they are and how they are used. Right off the bat, though, it states that the osmole is not an SI unit, and indeed the usual lists of derived ...
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Why convert to moles for stoichiometry calculations? [closed]

Why do you have to convert the reactants and products of an equation to moles when doing stoichiometry problems? Why can't you just convert straight to grams to solve the problem?
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How to determine the equation for the reaction of europium with sulfuric acid based on experimental measurements?

I was given a set of results by a fellow researcher where he reacted $0.608~\mathrm{g}$ of europium ($M = 152$) with an excess of $\ce{H2SO4}$ and collected $144~\mathrm{cm^3}$ of $\ce{H2}$ gas at ...