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3 years ago

14

If the half-life of a radioisotope is 20,000 years, then a sample in which three-quarters of that radioisotope has decayed is __

_________ years old

1 answer:

poizon [28]3 years ago

4 0

25% remaining = 40,000 years old

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22. Which statement best describes the use of catalytic converters in automobiles?

AysviL [449]

Answer:

B. They oxidize hydrocarbons to form less toxic gases.

Explanation:

A catalytic converter can be defined as an anti-pollution device containing a catalyst like platinum-iridium, installed in the exhaust chamber of an automobile so as to chemically convert harmful (poisonous) pollutants such as unburned hydrocarbons and carbon monoxide (CO), sulfur dioxide (S02), nitrogen oxide (NO) etc., into less harmful, poisonous or toxic chemical compounds.

This ultimately implies that, catalytic converters are typically used for converting harmful gases into less harmful, poisonous or toxic gases and molecules e.g carbon dioxide (C02) and water (H2O). This helps to prevent global warming, enhance the conservation of natural resources, as well as preserve the lives of living organisms and their natural habitat.

<em>Hence, the statement which best describes the use of catalytic converters in automobiles is that they oxidize hydrocarbons to form less toxic gases.</em>

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3 years ago

Darwin called this idea of certain traits being selected in order for an organism to reproduce sexual selection. In crickets and

tamaranim1 [39]

Th correct answer is option C. Calling can be hazardous because it also attracts parasites and predators.

The mating call is used by the males to attract females for sexual reproduction. By using vocal sounds males are not only making themselves attractive to females, they are also making themselves vulnerable to predators.

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Define atomic number

tester [92]

Answer:

the number of protons in the nucleus of an atom, which determines the chemical properties of an element and its place in the periodic table.

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When using 100ml or 50ml graduated cylinder to what decimal place can your volume be estimated?<br>

Olegator [25]

Answer:

I know that the 100-mL graduated cylinders are always read to 1 decimal place.

I think for 50 mL graduated cylinders, it lets you measure volumes up to 50.0 mL to the nearest 0.1 or 0.2 mL, depending on your exact cylinder.

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3 years ago

Write the isotopic symbol for the following (show your work) a) An isotope of iodine whose atoms have 78 neutrons b) An isotope

morpeh [17]

<u>Answer:</u>

<u>For a:</u> The isotopic representation of iodine is $_{53}^{131}\textrm{I}$

<u>For b:</u> The isotopic representation of cesium is $_{55}^{137}\textrm{Cs}$

<u>For c:</u> The isotopic representation of strontium is $_{38}^{52}\textrm{Sr}$

<u>Explanation:</u>

The isotopic representation of an atom is: $_Z^A\textrm{X}$

where,

Z = Atomic number of the atom

A = Mass number of the atom

X = Symbol of the atom

<u>For a:</u>

We are given:

Number of neutrons = 78

Atomic number of iodine = 53 = Number of protons

Mass number = 53 + 78 = 131

Thus, the isotopic representation of iodine is $_{53}^{131}\textrm{I}$

<u>For b:</u>

We are given:

Number of neutrons = 82

Atomic number of cesium = 55 = Number of protons

Mass number = 55 + 82 = 137

Thus, the isotopic representation of cesium is $_{55}^{137}\textrm{Cs}$

<u>For c:</u>

We are given:

Number of neutrons = 52

Atomic number of strontium = 38 = Number of protons

Mass number = 38 + 52 = 90

Thus, the isotopic representation of strontium is $_{38}^{52}\textrm{Sr}$

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3 years ago