1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Cloud [144]
3 years ago
6

A 5.00-mL sample of blood was treated with trichloroacetic acid to precipitate proteins. After centrifugation, the resulting sol

ution was brought to a pH of 3 and was extracted with two 5-mL portions of methyl isobutyl ketone containing the organic lead complexing agent APCD. The extract was aspirated directly into an air-acetylene flame yielding an absorbance of 0.454 at 283.3 nm. Five-milliliter aliquots of standard solutions containing 0.240 and 0.475 ppm Pb were treated in the same way and yielded absorbances of 0.412 and 0.642. Calculate the concentration Pb (ppm) in the sample assuming that Beer’s law is followed.
Chemistry
1 answer:
Anarel [89]3 years ago
3 0

Explanation:

According to the Beer-lambert' s law,

        Absrobance = absrobptitvity × lenght × concentration

So, if we will plot a graph between absrobance and concentration then we will obtain a straight line

Hence, formula to calculate slope of the graph is as follows.

   The slope of graph = \frac{\text{difference in absrobance at two points}}{\text{difference in concentrations at those points}}

The given data is as follows.

     A_{1} = 0.412 (first point)

     A_{2} = 0.642 (second point)

     C_{1} = 0.240 ppm (first point)

     C_{2} = 0.475 ppm (second point)

Hence, putting these values into the above formula we will calculate the value of slope as follows.

           Slope = \frac{\text{difference in absrobance at two points}}{\text{difference in concentrations at those points}}

                     = \frac{0.642 - 0.412}{0.475 - 0.240}

                      = \frac{0.23}{0.235}

                     = 0.978

It is known that for the graph, line equation can be written as follows.

                       y = mx + c  ........... (1)

where,      C = intercept

                 m = slope

Hence, calculate the value of intercept as follows.

           0.412 = 0.24 \times 0.978 + c

               c = 0.178

As it is given that the absorbance values 0.454 (the y-axis value). Therefore, putting this value into equation (1) we get the following.

                     y = mx + c

                  0.454 = x \times 0.978 + 0.178

                   0.276 = 0.978x

                         x = 0.282 ppm

Thus, we can conclude that the concentration of Pb in the given sample is 0.282 ppm.

You might be interested in
Can I please Get Help with this question ‍♂️ ?
Nitella [24]

Answer:

Mg(NO4)2 is 180.3 g/mol

Explanation:

First find the substance formula.

Magnesium Nitrate.

Magnesium is a +2 charge.

Nitrate is a -1 charge.

So to balance the chemical formula,

We need 1 magnesium atom for every nitrate atom.

2(1) + 1(-2) = 0

So the substance formula is Mg(NO4)2.

Now find the molar mass of Mg(NO4)2.

Mg = 24.3 amu

N = 14.0 amu

O = 16.0 amu

They are three nitrogen and twelve oxygen atoms.

So you do this: 24.3 + 14.0(2) + 16.0(8) = 180.3 g/mol

So the molar is mass is 180.3 g/mol.

The final answer is Mg(NO4)2 is 180.3 g/mol

Hope it helped!

7 0
3 years ago
Which element has atoms with only one completely filled principal energy level
liubo4ka [24]
I think it’s hydrogen
3 0
3 years ago
For the closed system below: Cu(s) + 2Ag+(aq) 2Ag(s) + Cu2+(aq) How would you know if the system is at equilibrium?
zaharov [31]
For the chemical reactiom to be at equilibrium:
1- The rate of forward reaction must be equal to the rate of the reverse reaction.
2- The mass of EACH element must be equal before and after the reaction (no NET change in mass), otherwise the equilibrium will shift.

Important note: you need to check the mass of each element before and after the reaction (i.e, reactants side and products side) and the not the mass of the system as a whole. This is because the mass of the whole system will be preserved whether the system is at equilibrium or not (this is the fundamental law of mass conservation)
5 0
3 years ago
The element lanthanum has two stable isotopes, lanthanum-138 with an atomic mass of 137.9 AMU and lanthanum-139 with an atomic m
dmitriy555 [2]

Answer:

A. there is an isotope of lanthanum with an atomic mass of 138.9

Explanation:

By knowing the different atomic masses of both Lanthanum atoms, we can not tell anything about their occurence in nature. Therefore, all the last three options are incorrect. Because, the atomic mass does not tell anything about the availability or natural abundance of an element.

Now, the isotopes of an element are those elements, which have same number of electrons and protons as the original element, but different number of neutrons. Therefore, they have same atomic number but, different atomic weight or atomic masses.

Hence, by looking at an elements having same atomic number, but different atomic masses, we can identify them as isotopes.

Thus, the correct option is:

<u>A. there is an isotope of lanthanum with an atomic mass of 138.9.</u>

7 0
3 years ago
An object on top of a building has a GPE of 23,048j and a mass of 39kg, What is the height of the object
kirill115 [55]

Answer:

<h2>59.1 m</h2>

Explanation:

The height of the object can be found by using the formula

h =  \frac{p}{mg }  \\

where

p is the potential energy

m is the mass

h is the height

g is the acceleration due to gravity which is 10 m/s²

From the question we have

h =  \frac{23048}{39 \times 10}  =  \frac{23048}{390}  \\  = 59.0974...

We have the final answer as

<h3>59.1 m</h3>

Hope this helps you

3 0
2 years ago
Other questions:
  • For the reaction A+B↽−−⇀C+D, assume that the standard change in free energy has a positive value. Changing the conditions of the
    8·1 answer
  • In the solid solution of a gold ring, which component is most likely the solvent?
    9·1 answer
  • Which option is an example of a chemical change?
    7·2 answers
  • A certain shade of blue has a frequency of 7.00 × 1014 Hz. What is the energy of exactly one photon of this light?
    8·2 answers
  • CuSO4.5H2O(k) ısı CuSO4(k) + 5 H2O(g) eşitliğine göre bakır sülfatın kristal suyu miktarı ve kaba formülü hesaplanacaktır.
    5·1 answer
  • Which allotrope of carbon is used in lubricants, sporting goods, and aircraft?
    5·1 answer
  • How many grams of chromium are in 2.0 x 1024 atoms
    13·1 answer
  • What do i do if my crush likes another girl?
    14·2 answers
  • Which type of model best represents simple molecules?
    7·2 answers
  • I don’t know what are the ones that are left ,can someone help me please
    6·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!