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horrorfan [7]
3 years ago
10

Americium-241 is used in smoke detectors. It has a first-order rate constant for radioactive decay of k = 1.6x10^−3yr−1. By cont

rast, iodine-125, which is used to test for thyroid functioning, has a rate constant for radioactive decay of k = 0.011 day−1.
(a) What are the half-lives of these two isotopes?
(b) Which one decays at a faster rate?
(c) How much of a 1.00-mg sample of each isotope remains after three half-lives?
(d) How much of a 1.00-mg sample of each isotope remains after 4 days?
Chemistry
1 answer:
Vika [28.1K]3 years ago
4 0

Answer:

A. 433 years and 63 days

B. Iodine

C. 0.125mg

D. 1.00mg

Explanation:

A. Americium

The formula of a radioactive decay constant half life is t = 0.693/k

Where k is the decay constant.

For americium, k = 0.0016

t = 0.693/0.0016 = 433.125 apprx 433 years

For iodine, k = 0.011

Half life = 0.693/0.011 = 63 days.

B. Iodine decays at a faster rate.

C. After three half lives

For both, first half life yields a mass of 0.5mg, next yields 0.25mg, next yield 0.125mg

D. 1.00mg still remains.

Half life is high for both so the decay after one day is insignificant.

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A 25 gram(m) metal ball is heated to 200C(delta T) with 2330 Joules(q) of energy. What is the specific heat of the metal?
Dominik [7]

Answer:

The specific heat of the metal is 0.466 \frac{J}{g*C}

Explanation:

Calorimetry is the measurement and calculation of the amounts of heat exchanged by a body or a system.

The equation that allows calculating heat exchanges is:

Q = c * m * ΔT

where Q is the heat exchanged by a body of mass m, made up of a specific heat substance c and where ΔT is the temperature variation.

In this case:

  • Q= 2330 J
  • c= ?
  • m= 25 g
  • ΔT= 200 °C

Replacing:

2330 J= c*25 g* 200 °C

Solving:

c=\frac{2330 J}{25 g* 200 C}

c=0.466 \frac{J}{g*C}

<u><em>The specific heat of the metal is 0.466 </em></u>\frac{J}{g*C}<u><em></em></u>

6 0
3 years ago
Read 2 more answers
Which elements have the most similar chemical properties
gtnhenbr [62]

Answer:

Elements that belong to the <em>same </em><em>GROUP</em><em> </em>of the periodic table have the most similar chemical properties.

Explanation:

A GROUP in the periodic table is a column of elements with the same number of valence electrons. Since electrons are exchanged/shared during a chemical reaction, then elements with similar valence electrons, will react similarly. Thus elements belonging to the <em>same GROUP</em> are most similar in the way they react.

For example: Sodium and Lithium are group 1 elements while fluorine and chlorine are group 17 elements. In a reaction under normal conditions, Sodium and Lithium will both try to give up their single valence electron to form cations. In doing so they will react more similarly. On the other hand, Fluorine and Chlorine who are more inclined to accept a single electron to form cations react less like the group 1 elements and more like each other.

6 0
3 years ago
Write the Noble Gas Notation for Silicone
ozzi

Answer:

[Ne] 3s2 3p2

Explanation:

Neon (Ne) is the noble gas right before silicon (Si).

Then right after neon is the 3s subshell. It has two electrons and is full.

After 3s comes the 3p subshell, and silicon only has two electrons in the 3p subshell (you can just count the electrons in each subshell on your periodic table).

8 0
3 years ago
A sample of a substance has a mass of 27.3 grams and a volume of 7.0 centimeters3. The density of this substance is
lora16 [44]

Answer:

The density of the substance is 3.9 grams per cubic centimeter.

Explanation:

Given mass=27.3 grams

volume=7 cubic centimeter

We need to find the density.

Density of a substance can be calculated by dividing mass of substance by volume of a substance  

Density\ =\ \frac{mass}{volume}

\\Therefore\ density\ =\ \frac{27.3}{7} \ =\ 3.9\ \frac{gm}{cm^3}

Hence Density of the substance is 3.9gm/cm^3.

4 0
3 years ago
Seasonal variation in Earth's climate are caused by
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B. Earth’s tilt

Earth’s tilt exposes different parts of the earth to varying degrees of sunlight throughout the year, causing seasons.
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