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Ivan
3 years ago
5

How long will it take for a 40.0 gram sample of I-131 (half-life = 8.4 days) to decay to 1/16 its original mass?

Chemistry
1 answer:
Shtirlitz [24]3 years ago
6 0

Answer:

42 days

Explanation:

Half life = 8.4 days

Starting mass = 40.0 g

Time = ?

Final Mass = 1/16 * 40 = 2.5 g

First Half life;

Remaining mass = 40 / 2 = 20g

Second Half life;

Remaining mass = 20 / 2 = 10g

Third Half life;

Remaining mass = 10 / 2 = 5g

Fourth Half life;

Remaining mass = 5 / 2 = 2.5g

Time = Number of half lives * Duration of half life = 5 * 8.4 = 42 days

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Give the name of one or more polysaccharides that matches each of the following descriptions:
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Answer:

A Cellulose not digested by humans.

b. the storage form of carbohydrates in plants is starch

C amylose contains 1-4 glycosidic bond

D Glycogen and starch are highly branched polysaccharides.

Explanation:

8 0
2 years ago
At 273 k and 1.00 x 10^-2 atm, the density of a gas is 1.24 x 10^-5 g/cm3.
bija089 [108]

Root mean square velocity is the square root of the mean of the squares of speeds of different molecules. From kinetic theory of gas, the formula of root mean square velocity=C_{rms}= √\frac{3RT}{M}=√\frac{3PV}{M}=√\frac{3P}{d}, where, R= Universal gas constant, T= Absolute temperature, P= Pressure, V= Volume of gas, d= Density of gas.

Given,  T=273 K, P=1.00 x 10⁻² atm, d=1.24 x 10⁻⁵ g/cm³.

(a) Using the formula C_{rms}=√\frac{3P}{d}=√(3X1.00X10⁻²)/(1.24X10⁻⁵)=49.18

(b) Molar mass can be determined by using the formula C_{rms}=√{3RT}{M}

49.18=√\frac{3X8.314X273}{M}

49.18²=√(3X8.314X273)/M

M=\frac{3X8.314X273}{49.18^{2} }

M=1.67 ≅ 2

Molecular mass is 2.

(c) The gas is Helium (He) whose molecular mass is 2.

8 0
3 years ago
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AfilCa [17]
I think it’s salt water
7 0
3 years ago
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The element carbon exists in several different forms. Pure carbon can be found in the form of diamonds, coal, and the graphite i
UNO [17]

Answer:

B) All carbon atoms have 6 neutrons.

Explanation:

The false statement from the given choices is that all carbon atoms have 6 neutrons.

There is a phenomenon called isotopy in chemistry.

Isotopy is the existence of two or more atoms of the same element having the same atomic number but different mass numbers due to the differences in the number of neutrons in their various nuclei.

  • These atoms of elements are called isotopes.
  • Carbon atoms generally have proton number of 6 which is the same as the atomic number.
  • As with all atoms, the mass number or atomic mass equals the number of protons and neutrons.

For the isotopes of carbon, their number of neutrons differs.

 For example:

            <em>¹²₆C                           ¹³₆C                        ¹⁴₆C</em>

The number of neutrons differs in the above isotopes.

 Number of neutrons = mass number - atomic number;

    ¹²₆C  , number of neutrons  = 12 - 6  = 6

      ¹³₆C, number of neutrons  = 13 - 6  = 7

       ¹⁴₆C, number of neutrons = 14 - 6  = 8

Therefore, based on the concept of isotopy, all carbon atoms do not have 6 neutrons.

7 0
3 years ago
Water is formed when two hydrogen atoms bond to an oxygen atom. The hydrogen and the oxygen in this example are different A) com
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Hydrogen and oxygen are elements.
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