# ¿A shaker of salt substitute contains 1.6 oz of K. What is the activity, in milliCuries, of the potassium in the shaker? The activity is 7 microcuries (µCi)

2 months ago

## Solution 1

Guest #3859
2 months ago
We know K-40 (potassium having atomic mass 40 g) is radioactive and its natural abundance is 0.012%
So for 1 mol of potassium contains 0.00012 mol of K-40
Now 1.6 oz of K = 45.36 g of K
average atomic weight of K = 39.1 g
so 45.36 g of K contains:
(45.36 / 39.1) * 0.00012 * 6.022 x 10²³ (atoms of K-40)
= 8.4 x 10¹⁹ atoms of K-40
We know, activity A is:
A = 0.693 / t1/2 N₀
[t1/2 : half life time and N₀ : initial number of atoms]
t1/2 of K-40 = 1.28 x 10⁹ years
= 4.04 x 10¹⁶ seconds
So A = (0.693 / 4.04 x 10¹⁶) * (8.4 x 10¹⁹ ) = 1441 cps
A = 141 x (1/3.7 x 10¹⁰)   because 3.7 x 10¹⁰ cps = 1 Ci
A = 3.9 x 10⁻⁸ Ci  = 3.9 x 10⁻⁵ millicurie

## 📚 Related Questions

Question
A chemistry student mixes 5 grams of sodium chloride (NaCl) in 100 ml of water and stirs until all of the salt is dissolved. Once dissolved, the student measures the electrical conductivity of the solution. An additional 5 grams of NaCl is then dissolved in the solution. Which statement MOST accurately describes how the additional five grams of salt will affect the electrical conductivity of the solution?
Solution 1

When additional 5 grams of NaCl are dissolved in solution the conductivity of solution increases as more ions are available for conduction.

### What are ions?

An ion is defined as an atom or a molecule which has a net electrical charge. There are 2 types of ions :1) cation 2) anion . The cation is the positively charged ion and anion is the negatively charged ion . As they are oppositely charged they attract each resulting in the formation of ionic bond.

Ions consisting of single atom are mono-atomic ions while which consists of two or more ions are called as poly-atomic ions . They are created by chemical interactions . They are very reactive in their gaseous state and rapidly react with  the oppositely charged ions resulting in neutral molecules.

brainly.com/question/1488567

#SPJ2

Solution 2
I think the best choice is
A) The conductivity of the solution will increase because more ions are being added to the solution.
Because number ions will be increased, but big amount of NaCl can be still dissolved.
Question
James is looking at a parallel circuit plan for lighting. There is a battery providing the power. There are switches labeled A,B,C,D that can be turned on to close the circuit. Which switch does not have to be on for light 3 to function?
Solution 1
The answer is D because for light 3 to function switch d does not  have to turn on
Solution 2

For light 3 to function, switch D does not have to be on. This diagram shows a parallel circuit that provides more than one way for the current to return to the power source.

Question
Which of the following naturally orccuing radioisotopes would be most useful in dating objects
Solution 1
Potassium -40half life = 1.28 ×10∧9.
Radioisotope can be used to determine the age of fossils, to treat skin disease, to sterilize foodstuffs, and also to sterilize surgical instruments.
Radioisotope dating is a way to estimate a fossil's age by a method of analyzing the elemental isotopes which are within the rocks which it is in.
Question
Which statement describes a gas condensing into a liquid?
Solution 1

The molecules get closer together and move more slowly.

Explanation:

from a gas to a liquid, the atoms or molecules of the substance do not change. Instead, the motion of the atoms or molecules in the substance determines its state of matter.

gas condenses to form a liquid, the molecules get closer together and move more slowly. If the molecules continue to slow down until they move so slowly that they can only vibrate against one another, then the substance becomes a solid.

Solution 2
Condensation / hope this helps !
Question
Which of the following describes an air mass with the symbol cT? a. it is a cold air mass over an ocean c. it is a warm air mass over an ocean b. it is a warm air mass over a continent d. it is a cold air mass over a continent
Solution 1

It is a warm air mass over a continent describes an air mass with symbol cT.

### What is air mass?

An air mass is a sizable portion of the atmosphere that has a largely constant temperature and moisture content. Air masses can travel thousands of kilometers in either direction and can extend up to 16 km (10 mi) into the atmosphere, or the stratosphere.

Large, uniformly-cooled and humid surfaces are known as source zones where air masses form. Low wind speeds allow air to remain still for an extended period of time and absorb the characteristics of the source region, such as heat or cold.

The weather characteristics of this air mass depend on how long of a sea track it takes to travel from Europe to the British Isles. Because this air is naturally very cold and dry, if it travels only a short distance over.

Therefore, It is a warm air mass over a continent describes an air mass with symbol cT.

brainly.com/question/12089291

#SPJ3

Solution 2

B) Warm air mass over a continent

Explanation:

cT means Tropical c= continent

Question
Which of the following gases is NOT found in Earth’s atmosphere? a. oxygen c. hydrogen b. nitrogen d. all of the above are in the atmosphere
Solution 1
The answer is D. All of the above.
Solution 2
D. all of the above are in the atmosphere
Question
How many sucrose molecules are in 3.0 moles of sucrose scientific
Solution 1
1.80 × 10²⁴ Molecules of Sucrose

Solution:

Number of Moles and Number of Particles (molecules in given case) are related to each other as,

Moles  =  Number of Molecules ÷ 6.022 × 10²³

Solving for Number of Molecules,

Number of Molecules  =  Moles × 6.022 × 10²³

Data Given;
Moles  =  3 moles

Putting values in eq,

Number of Molecules  =  3 mol × 6.022 × 10²³

Number of Molecules  =  1.80 × 10²⁴ Molecules
Solution 2

Explanation:

Question
The periodic trend for electronegativity is similar to what other trend? A. The trend for shielding. B. The trend for ionic radii C. The trend for atomic radii D. The trend for first ionization energy
Solution 1

Option D: The trend for first ionization energy.

Electronegativity is defined as tendency of an atom of element to attract electron pair towards itself. On moving left to right in a period, electronegativity increases  due to increase in nuclear charge and on moving top to bottom in a group, it decreases due to increase of distance between nucleus and outermost shell.

Shielding decreases with increase in electronegativity. If the nuclear charge gets shielded by inner electrons, outer electrons will experience less nuclear charge and the tendency of an atom to attract electron/s decreases or electronegativity decreases. Thus, electronegativity trends can not be similar to the trends of shielding. Option A is wrong.

Ionic radius is defined as distance between the nucleus and outermost shell of an ion (charged atom) and atomic radius is distance between the nucleus and outermost shell of an atom. On moving left to right in a period, atomic and ionic radius decreases because  nuclear charge increases and it pulls the outer electrons more towards itself resulting decrease in size. Similarly, on moving top to bottom in a group, atomic and ionic radius increases due to addition of an extra period. Therefore, option B and C are wrong.

Ionization energy is the amount of energy needed to remove an electron from outer most shell of an atom. On moving left to right in a period, it increases due to increase in  nuclear charge, as outer electrons are more attracted to the nucleus. On moving top to bottom, due to increase in size, ionization energy decrease because small amount of energy is required to remove the outer shell electron/s. Therefore, trends for first ionization energy are similar to electronegativity trends and option D is correct.

Solution 2
D. The trend for first ionization energy
Question
Which of the following properties increases down the periodic table? A. Number of valence electrons B. Electronegativity C. Atomic radius D. Ionization energy
Solution 1
Atomic radius increases as you go down the periodic table.
Question
When water reaches its boiling point and turns into water vapor what happens to the molecules structure
Solution 1
The molecular structure will remain the same.

Explanation:
When water is heated, the heat supplied breaks down the intermolecular interactions (Hydrogen bondings) between the water molecules. This results in conversion of liquid state to gas state and water vapors evaporate.
While the molecular structure keeps intact. It is not changed. Hence, when the heat is removed the vapors of water condense back to liquid state and releases the heat which was absorbed during vaporization.

2647929
842281
748681
586256
406852
368373
348603
324927
199835
130075
112100
106146
77164
23213
22589
19607
17108
13966
10987
3389
{"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0}