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.

Filter by
Sorted by
Tagged with
1
vote
1answer
158 views

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 ...
1
vote
0answers
27 views

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 ...
3
votes
1answer
2k views

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-...
-2
votes
1answer
15k views

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 ...
2
votes
2answers
102 views

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 ...
9
votes
2answers
1k views

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 ...
-3
votes
1answer
3k views

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.
0
votes
1answer
12k views

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/...
-3
votes
2answers
271 views

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. ...
-4
votes
1answer
371 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 ...
0
votes
1answer
1k views

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 ...
-2
votes
2answers
5k views

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 ...
0
votes
1answer
111 views

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 ? ...
-9
votes
1answer
11k views

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 ...
2
votes
3answers
232 views

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 ...
-2
votes
1answer
1k views

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?
8
votes
6answers
4k views

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 ...
8
votes
1answer
768 views

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 ...
17
votes
7answers
10k views

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 ...
-1
votes
1answer
11k views

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?
1
vote
1answer
2k views

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 ...
3
votes
2answers
666 views

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? ...
1
vote
1answer
262 views

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....
0
votes
1answer
2k views

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 ...
0
votes
2answers
45k views

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. ...
0
votes
2answers
969 views

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 ...
2
votes
1answer
3k views

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^{...
0
votes
1answer
354 views

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 ...
3
votes
2answers
11k views

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 ...
1
vote
0answers
55 views

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 ...
2
votes
1answer
2k views

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 ...
2
votes
2answers
332 views

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 ...
-1
votes
6answers
5k views

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?
1
vote
1answer
3k views

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 ...
-4
votes
1answer
105 views

Why is Avogadro's statement true that at STP conditions all matter have same number of atoms or molecules?

As atomic number increases, atomic size, number of electrons and shells also increase. So due to higher atomic size and maximum number of electrons, there should be maximum repulsion forces between ...
0
votes
2answers
3k views

Volume of one equivalent of a gas

How do we define an equivalent when we are not talking about any particular reaction? Like, we say that equivalent volume of Oxygen is 5.6L, so we have taken the n-factor to be 4, and in CO2 we take n-...
0
votes
1answer
386 views

Calculating molar mass from gas data

34.05 mL of phosphorus vapour weighs 0.0625 g at 546 °C and 0.1 bar pressure. What is the molar mass of phosphorus? I tried to solve the above question and got 1249.8g. The book's answer sheet lists ...
1
vote
1answer
161 views

Find the amount of atoms for a given mass

The atomic mass of two elements A and B is 40 and 80 respectively. If x g of A contains y atoms, how many atoms are present in 2x g of B? I have tried to solve by assuming that x g of A has y atoms ...
0
votes
2answers
758 views

Why do we assume that it is 1 mol?

A question in my book was as following: Benzine and chloroform are considered very toxic organic solvents that dissolve in each other and in a solution of benzine and chloroform there is 0.45 mol ...
2
votes
1answer
112 views

Number of water molecules to contribute one molecule to every milliliter on earth

How many millilitres of water would it take so that, when they are thoroughly dispersed around the world, it would yield an average of one molecule of the original sample of water in each millilitre ...
3
votes
1answer
981 views

Raoult's Law and Mole Fraction

Raoult's Law states that the partial vapor pressure of each component of an ideal mixture of liquids is equal to the vapor pressure of the pure component multiplied by its mole fraction in the mixture....
-1
votes
2answers
4k views

How to calculate the mass of a single atom?

If we know the molar mass of a certain element and Avogadro's constant, how can we calculate the mass of a single atom? Do we need to multiply the molar mass with Avogadro's constant?
0
votes
1answer
5k views

How to calculate the maximum number of molecules or ions from a given amount of substance?

Which of the following solutions has the greatest number of particles (atoms or ions) of solute per liter? (a) $1~\mathrm{M}\ \ce{NaCl}$ (b) $1~\mathrm{M}\ \ce{CaCl2}$ (c) $1~\mathrm{M}$ ethanol (d) $...
0
votes
1answer
101 views

Calculate the heat of a reaction

Say I would like to calculate the heat produced by the following reaction: $$\ce{2SO2 + O2\longrightarrow2SO3}$$ I have calculated the moles of the reagents. I can't seem to figure out how to ...
0
votes
1answer
787 views

How to calculate a molar mass based on density?

I have been asked to calculate the molar mass and mole fraction of a 35 w/w% HClO4 solution with a density of 1.3g per ml. This is the equation I used to try to solve it: $\frac{1}{M} = \frac{0.35}{...
2
votes
1answer
502 views

Is this definition of mole correct?

Chemical engineers define one mole as the amount of a substance which possess as many entities as $12\ \mathrm g$ of $\ce{^{12}C}$. The number of atoms in $12\ \mathrm g$ of $\ce{^{12}C}$ is $6.022 \...
3
votes
1answer
774 views

Determining water of crystallisation in a hydrate from the mass percentages

How would I find the amount of water in a hydrate if all I was given was the mass percentage of one element in the compound? For example, a question asks: $\ce{Zn(ClO3)2. $x$H2O}$ contains $21.5\%$ ...
1
vote
0answers
1k views

Ratios and mass; reaction calculation problem

I have come across the following problem: One method used to inflate air bags in cars is to use nitrogen produced chemically from the decomposition of sodium azide. The sodium formed reacts with ...
1
vote
1answer
511 views

pH of a mixture of base and an acid

I have the following question: Assume that you have two solutions. One of $50\ \mathrm{cm^3}$ $\ce{HCl}$ $\mathrm{pH} = 1.3$ and one of $150\ \mathrm{cm^3}$ $\ce{Ba(OH)2}$ $\mathrm{pH} = 12.3$. If we ...
2
votes
1answer
8k views

How many grams of sodium sulfate and water in 100ml of 0.5M solution

Calculate how many grams of sodium sulfate ($\ce{Na2SO4}$) and water ($\ce{H2O}$) should be used to prepare $\pu{370 g}$ of 15% solution of this salt. How many mL of this 15% solution should be taken ...