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just olya [345]
3 years ago
9

What element has a half-life = to 64

Chemistry
1 answer:
Virty [35]3 years ago
5 0
The best answer is the isotope of strontium which is strontium-85. It has a half-life of about 64 days. The metal strontioum has four stable, naturally occurring isotopes which includes 84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%).
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Why do different chemicals emit different colors of light?​
Mama L [17]

Answer:

Because no two elements have the same set of energy levels, different elements emit different colors of light. Energy is released when electrons move from higher energy levels to lower ones (visible light).

Explanation:

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3 years ago
Name four types of pathogens that could cause infectious disease??
Kryger [21]
Bacteria, virus, fungi, and protists are the four pathogens.
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3 years ago
Proportional means that
FromTheMoon [43]
Corresponding in size or amount to something else.
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3 years ago
From 1962 until 1981 pennies were made from 95% copper and 5% zinc and had a mass of 3.1 g. Starting in 1982, pennies have been
Sloan [31]

Answer:

2.7724 g

Explanation:

Mass of pre- 1892 pennies = 3.1 g

Abundance = 45.4 %

Mass of post 1892 pennies = 2.5 g

Abundance = 100 - 45.4 = 54.6 %

The average mass is given as = ( 3.1 g   *  45.4 / 100)  +  (2.5g  *  54.6 / 100)

Average Mass = 3.1 * 0.454   +   2.5  *  0.546

Average Mass = 1.4074  + 1.365 = 2.7724 g

8 0
3 years ago
A piece of iron is heated to 95.0 celsius and then placed in an insulated vessel containing 250. grams of water at 25.0 celsius.
Nana76 [90]

Answer:

c) 387g

Explanation:

Water;

Mass = 250g

Specific heat = 4.184

Initial Temp, T1 = 25 + 273 = 298K

Final Temp, T2 = 35 + 273 = 308K

Heat = ?

H = mc(T2 - T1)

H = 250 * 4.184 (308 - 298)

H = 10460 J

Iron;

Initial Temp, T2 = 95 + 273 = 368K (Upon converting to kelvin temperature)

Mass = ?

Final Temp, T1 = 35 + 273 = 308

Heat = 10460 (Heat lost by iron is qual to heat gained by water)

Specific heat = 0.45

H = mc(T2-T1)

M = 10460 / [0.45 (308 - 368)]

M = 10460 / 27

M = 387g

7 0
2 years ago
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