stoichiometry?

Question

okay here's the question, it's kind long:

Bees releasse about 1.0 x 10^ -6 g of isopentyl acetate. How many molecules of isopentyl acetate (C7H14O2) are released in a typical bee sting? How many atoms of carbon are present?

Answer 1

Okay. So let's break your molecule down:

C7 = 7 x 12 g/mol = 84 g/mol
H14 = 14 x 1 g/mol = 14 g/mol
O2 = 2 x 16 g/mol = 32 g/mol

So the molar mass of your molecule is 130 g/mol. If a sting releases 1.0 x10^-6 g, then...

(1.0 x10^-6 g) x (1 mol/130 g) = 7.7 x10^-9 moles

...and since 1 mole is 6.022 x10^23...

(7.7 x10^-9 mol) x (6.022 x10^23 molecules/mol) = 4.6 x10^15 molecules

So that's your answer for the first part. And since each molecule of isopentyl acetate has seven carbon atoms, there are seven times that number, or 3.2 x10^16 carbon atoms.

Hope that helps!

Answer 2

Isopentyl acetate C7 H14 O2

Check the periodic table for the atomic weights of each element.

C = 12.0107 amu X 7 = 84.0749

H = 1.00794 amu X 14 = 14.11116

O = 15.9994 amu X 2 = 39.9988

The atomic mass unit for isopentyl acetate is 84.0749+ 14.11116+39.9988 = 138.18486 or 138.1849 if we look at significant figures.

The amounts of carbon in isopetyle acetate is 84.0749/138.18486 = 60.8%

1.0 x10^-6 grams would be 1.0 X10^-6 * 60.8% = 6.08 X 10^-5 grams

Avogadro's number is the number of atoms in an atomic mass unit. 6.0221415×10^23

Carbons atomic mass unit is 12.0107 grams.

6.08 X 10^-5/ 12.0107 = X/6.0221415×10^23

X= 6.0221415×10^23 * 6.08 X 10^-5 / 12.0107

X= 3.04 x 10^18 atoms

Check my math, I don't have a scientific calculator here.

Answer 3

C'mon, do it yourself! That is the only way to learn the material you need in first year chemistry. If you are stuck, ask for help with the thinking needed to solve it, don't just look for an answer.

In this case, you are given a mass, and from a mass of substance, you have to first convert it to the number of moles of the substance. You can figure out how to do this by looking at the units, then figuring out how to multiply quantities together so the units cancel to give you what you need.

In this case, you want to go from grams -> moles. This is done using the conversion factor of grams/mole, which is the molecular mass of isopentyl acetate. (to get this number, add up the atomic masses of carbon, hydrogen and oxygen in the molecular formula.)

So, 1 x 10^-6 g X (mole/ g) = grams cancel leaving you with moles.

Once you have moles, you want to go from moles -> molecules and you do this using the conversion factor that tells you how many molecules are in a mole.

X moles times (6.02 x 10^23 molecules/mole) = mole cancel leaving with molecules.

Then you need to go from molecules -> atoms, and you use the conversion factor that tells us how many atoms in each molecule of bee sting.

Got it? You do it.

Answer 4

How many molecules?
First, we need to convert from grams to molecules. Conversion from mass to molecules is a two-step process: step 1 is to convert grams to moles using the molecular weight of isopentyl acetate; step 2 is to convert moles to molecules using Avogadro's number.
The molecular weight of isopentyl acetate is 130.19 g/mol. Dividing the mass by the molecular weight gives:
1.0 x 10^-6 g / 130.19 g/mol = 7.6811 x 10^-9 moles
To convert moles to molecules, multiply by Avogadro's number:
7.6811 x 10^-9 mol * 6.0221 x 10^23 molecules/mol= 4.6526 x10^15 molecules
There are 2 significant figures in the mass of isopentyl acetate given, so we should report 2 significant figures:
4.7 x10^15 molecules of isopentyl acetate

How many atoms of carbon?
To calculate this, we must use the molecular formula: C7H14O2. The C7 tells us there are 7 atoms of carbon in each molecule. So, the number of carbon atoms is just seven times the number of molecules:
4.6526 x10^15 molecules * 7 carbon atoms/molecule = 3.2379 x10^16 carbon atoms
Again, we should round off to only 2 significant figures:
3.2 x10^16 carbon atoms

(NOTE: this answer only tells the number of carbon atoms in the isopentyl acetate and ignores carbon atoms in the bee sting present in other molecules.)

Answer 5

Its preety easy: what is the number of moles produced:
n= mass/Molecular mass. n= 1.0x10^-6g/ 130.21gmol^-1
equals 7.67x10^-8moles
for the number of carbons C7= 7 x number of moles
equals 5.375 x10^-7

Hope this helps you :)

Answer 6

what number moles of nitrogen and hydrogen are required to make one mole of ammonia, NH3? equation N2 + 3H2 = 2NH3 so dividing through 2 to get one mole of NH3 provides a million/2 mole of N2 and three/2 mole of H2

Answer 7

bad in school?