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Kobotan [32]
3 years ago
15

You want to determine the protein content in milk with the Kjeldahl method. You take 100 g whole milk and use 100 mL of 0.5 M hy

drochloric acid to collect ammonia. You needed 34.50 mL of 0.3512 M NaOH for the back-titration. Calculate the percentage of protein in the sample where CP = 6.38 (that is % protein = CP x %N).
Chemistry
1 answer:
stepladder [879]3 years ago
6 0

Answer:

3.38%

Explanation:

Given that;

the mass of the whole milk sample = 100 g

volume of HCl = 100 mL = 0.1 L

molarity of HCl = 0.5 M

volume of NaOH = 34.50 mL = 0.0345 L

molarity of NaOH = 0.3512 M

Since we knew the molarity and volume of both HCl and NaOH; we can calculate their corresponding number of moles present.

So, number of moles of HCl = molarity of HCl × volume of HCl

number of moles of HCl = 0.5 M ×  0.100 mL

                                        = 0.05 mole

number of moles of NaOH = Molarity of NaOH ×  Volume of NaOH

number of moles of NaOH = 0.3512 M ×  0.0345 L

                                            = 0.012 mole

From the question, we can deduce that the number of HCl that is consumed by NH₃ is equal to the number of moles of HCl that is consumed by NaOH.

SO, number of moles of HCl consumed by NH₃ = Total moles of HCl - moles of HCl consumed by NaOH

= 0.05 mole - 0.012 mole

= 0.038 mole

However, to determine the mole of NH₃ present , we have:

number of moles of NH₃ present = number of moles of HCl consumed by NH₃  = 0.038

∴ the mass of Nitrogen with the molecular weight (14.0 g/mol) = 0.038 moles × 14.0 g/mol

= 0.530 g

Now, the percentage of Nitrogen can be calculated as;

percentage of nitrogen =\frac{mass of nitrogen}{mass of the whole milk sample} *100

percentage of nitrogen =\frac{0.530g}{100g} *100

percentage of nitrogen =0.530%%

the percentage of protein in the sample = CP × %age of N

where CP is given as 6.38

∴ the percentage of protein in the sample = 6.38 ×  0.530%

the percentage of protein in the sample = 3.3814%

the percentage of protein in the sample = 3.38%

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Significant digits are the number of digits that reflect the precision of a measurement or number.
Delvig [45]

Answer:

True

Explanation:

Significant digits are numbers that helps to present the precision of measurements calculations.

Numbers that do not contribute to the precision of a reading should not be counted as significant.

There are rules of assigning significant numbers:

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5 0
3 years ago
What is the correct iupac name of CH3-CH2-CH2CHO ?
kow [346]

the correct IUPAC name of the compound is 1-Butanal.

<h3>What are IUPAC names?</h3>

It is a system of naming organic compounds based on the longest carbon-to-carbon single bonds. It does not matter whether these longest chains are continuous or in a ring.

Thus, when the compound with the chemical formula, CH3-CH2-CH2CHO is considered. The longest carbon-to-carbon chain is 4. The 1st carbon carries a functional group known as an aldehyde.

Aldehydes are equipped with the carbonyl group and have the general formula R−CH=O. They are also sometimes referred to as formyl.

Aldehydes are named after their parent alkane chains with a slight modification. The 'e' is replaced with 'al'

The aldehyde in this case has four carbons. This means that the parent alkane is Butane. Therefore, the name of the compound will be 1-Butanal.

More on IUPAC names can be found here: brainly.com/question/16631447

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4 0
2 years ago
The radioactivity due to carbon-14 measured in a piece of a wooden casket from an ancient burial site was found to produce 20 co
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Answer:

17202.6 years

Explanation:

Activity of the living sample (Ao) = 160 counts per minute

Activity of the wood sample (A) = 20 counts per minute

Half life of carbon-14 = 5730 years

t= age of the artifact

From;

0.693/t1/2= 2.303/t log Ao/A

Then;

0.693/ 5730= 2.303/t log Ao/A

Substituting values;

0.693/5730= 2.303/t log (160/20)

Then we obtain;

1.209×10^-4 = 2.0798/t

t= 2.0798/1.209×10^-4

Thus;

t= 17202.6 years

Therefore the artifact is 17202.6 years old.

3 0
3 years ago
How do you find the amount of moles is .032 grams of water and whats the answer
masha68 [24]

Answer:

\boxed {\boxed {\sf 0.0018 \ mol \ H_2 O }}

Explanation:

First, we need to find the molecular mass of water (H₂O).

H₂O has:

  • 2 Hydrogen atoms (subscript of 2)
  • 1 Oxygen atom (implied subscript of 1)

Use the Periodic Table to find the mass of hydrogen and oxygen. Then, multiply by the number of atoms of the element.

  • Hydrogen: 1.0079 g/mol
  • Oxygen: 15.9994 g/mol

There are 2 hydrogen atoms, so multiply the mass by 2.

  • 2 Hydrogen: (1.0079 g/mol)(2)= 2.0158 g/mol

Now, find the mass of H₂O. Add the mass of 2 hydrogen atoms and 1 oxygen atom.

  • 2.0158 g/mol + 15.9994 g/mol = 18.0152 g/mol

Next, find the amount of moles using the molecular mass we just calculated. Set up a ratio.

0.032 \ g  \ H_2 O* \frac{ 1 \ mol \ H_2 O}{18.0152 \ g \ H_2 O}

Multiply. The grams of H₂O will cancel out.

0.032 * \frac{1 \ mol \ H_2 O}{18.0152 }

\frac{0.032 *1 \ mol \ H_2 O}{18.0152 }

0.00177627781 \ mol \ H_2 O

The original measurement given had two significant figures (3,2). We must round to have 2 significant figures. All the zeroes before the 1 are not significant. So, round to the ten thousandth.

The 7 in the hundred thousandth place tells us to round up.

0.0018 \ mol \ H_2 O

There are about <u>0.0018 moles in 0.032 grams.</u>

6 0
3 years ago
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