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kirill115 [55]
3 years ago
14

If 50% of a radioactive element remains after 4000 years, what is the half-life?

Chemistry
1 answer:
ANTONII [103]3 years ago
4 0

Hey there!

A half-life means after a certain amount of time, half of that substance will be gone/changed after that time.

If 50%, or half, of the element remains after 4000 years, that means the half life must be 4000 years.

Hope this helps!

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Calculate the moles of calcium chloride (CaCl2) needed to react in order to produce 85.00 grams of calcium carbonate (CaCO3). us
BartSMP [9]

Answer:

0.85 mole

Explanation:

Step 1:

The balanced equation for the reaction of CaCl2 to produce CaCO3. This is illustrated below:

When CaCl2 react with Na2CO3, CaCO3 is produced according to the balanced equation:

CaCl2 + Na2CO3 -> CaCO3 + 2NaCl

Step 2:

Conversion of 85g of CaCO3 to mole. This is illustrated below:

Molar Mass of CaCO3 = 40 + 12 + (16x3) = 40 + 12 + 48 = 100g/mol

Mass of CaCO3 = 85g

Moles of CaCO3 =?

Number of mole = Mass /Molar Mass

Mole of CaCO3 = 85/100

Mole of caco= 0.85 mole

Step 3:

Determination of the number of mole of CaCl2 needed to produce 85g (i.e 0. 85 mole) of CaCO3.

This is illustrated below :

From the balanced equation above,

1 mole of CaCl2 reacted to produced 1 mole of CaCO3.

Therefore, 0.85 mole of CaCl2 will also react to produce 0.85 mole of CaCO3.

From the calculations made above, 0.85 mole of CaCl2 is needed to produce 85g of CaCO3

5 0
3 years ago
Read 2 more answers
Sixty liters of a gas were collected over water when the barometer read 663 mmhg , and the temperature was 20∘c. what volume wou
lesya [120]
First, let's compute the number of moles in the system assuming ideal gas behavior. 

PV = nRT
(663 mmHg)(1atm/760 mmHg)(60 L) = n(0.0821 L-atm/mol-K)(20+273 K)
Solving for n,
n = 2.176 moles

At standard conditions, the standard molar volume is 22.4 L/mol. Thus,

Standard volume = 22.4 L/mol * 2.176 mol =<em> 48.74 L</em>
3 0
3 years ago
12. How are secondary sources of energy different from other energy resources?<br> (Plz help)
Pani-rosa [81]

Answer:

Explanation:Energy is the capacity of a physical system to perform work. Energy exists in several forms such as heat , kinetic or mechanical energy, light, potential energy , electrical, or other forms. Energy is the ability to do work. Energy sources could be classified as Renewable and Non-renewable.

7 0
3 years ago
What would happen if the Earth was tilted more than its current tilt of 23.5°? <br><br> HELP ASAP!!
Oduvanchick [21]

Answer:

Wouldn't the Earth's atmosphere be moving too fast that it eventually breaks out?

Explanation:

Do NOT trust me.

7 0
2 years ago
PLEASE HELP ME THIS IS DUE RN I HAVE NO IDEA I WILL MARK BRAINLIEST I JUST NEED HELP
djverab [1.8K]

Answer:

3.45 × 10^5

=3.45^5

I hope this helps

6 0
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