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NARA [144]
3 years ago
7

Round off 808.57 to 4 significant figures.

Chemistry
1 answer:
Marysya12 [62]3 years ago
4 0

Answer:

808.6

Explanation:

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A 0.1510 gram sample of a hydrocarbon produces 0.5008 gram CO2 and 0.1282 gram H2O in combustion analysis. Its
Over [174]
In a combustion of a hydrocarbon compound, 2 reactions are happening per element:

C + O₂ → CO₂
2 H + 1/2 O₂ → H₂O

Thus, we can determine the amount of C and H from the masses of CO₂ and H₂O produced, respectively.

1.) Compute for the amount of C in the compound. The data you need to know are the following:
Molar mass of C = 12 g/mol
Molar mass of CO₂ = 44 g/mol
Solution:
0.5008 g CO₂*(1 mol CO₂/ 44 g)*(1 mol C/1 mol CO₂) = 0.01138 mol C
0.01138 mol C*(12 g/mol) = 0.13658 g C

Compute for the amount of H in the compound. The data you need to know are the following:
Molar mass of H = 1 g/mol
Molar mass of H₂O = 18 g/mol
Solution:
0.1282 g H₂O*(1 mol H₂O/ 18 g)*(2 mol H/1 mol H₂O) = 0.014244 mol H
0.014244 mol H*(1 g/mol) = 0.014244 g H

The percent composition of pure hydrocarbon would be:
Percent composition = (Mass of C + Mass of H)/(Mass of sample) * 100
Percent composition = (0.13658 g + 0.014244 g)/(<span>0.1510 g) * 100
</span>Percent composition = 99.88%

2. The empirical formula is determined by finding the ratio of the elements. From #1, the amounts of moles is:

Amount of C = 0.01138 mol
Amount of H = 0.014244 mol

Divide the least number between the two to each of their individual amounts:
C = 0.01138/0.01138 = 1
H = 0.014244/0.01138 = 1.25

The ratio should be a whole number. So, you multiple 4 to each of the ratios:
C = 1*4 = 4
H = 1.25*4 = 5

Thus, the empirical formula of the hydrocarbon is C₄H₅.

3. The molar mass of the empirical formula is

Molar mass = 4(12 g/mol) + 5(1 g/mol) = 53 g/mol
Divide this from the given molecular weight of 106 g/mol
106 g/mol / 53 g/mol = 2
Thus, you need to multiply 2 to the subscripts of the empirical formula.

Molecular Formula = C₈H₁₀

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3 years ago
Select the correct answer. What happens when an electron absorbs energy? A. The electron moves from a lower energy orbital to a
umka2103 [35]
I choose the option A.
The electron absorbs energy from specific wavelength then moving from a lower energy orbital to a higher energy orbital.
3 0
2 years ago
In an experiment, the molar mass of the compound was determined to be 118.084 g/mol. What is the molecular formula of the compou
pishuonlain [190]

Answer:

Succinic acid

Explanation:

The most common possibility is succinic acid

As it has decimals after whole no till hundredth it contains OH and C in most of the cases .

Let's check for succinic acid

  • C4H_6O_6
  • 4(12)+4(16)+6
  • 64+48+6
  • 118u

Yes approximately equal

Molecular formula is.

(CH_2)_2(CO_2H)_2

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2 years ago
Please help me with my 8th grade chemistry, I'm behind and don't understand it at all
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When a material is heated, the kinetic energy of that material increases and its atoms and molecules move about more. This means that each atom will take up more space due to its movement so the material will expand. ... Some metals expand more than others due to differences in the forces between the atoms / molecules.

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