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Harrizon [31]
3 years ago
11

The half-life for the radioactive decay of calcium-47 is 4.5 days. how many half-lives have elapsed after 27 days?

Chemistry
2 answers:
Evgesh-ka [11]3 years ago
8 0
1 half-life      - 4.5 days
x half-lives   - 27 days

x=(1*27)/4.5=6
6 <span>half-lives have elapsed after 27 days.</span>
Pani-rosa [81]3 years ago
6 0

<u>Answer:</u> The number of half lives are 6

<u>Explanation:</u>

We are given:

Half life of a radioactive isotope = 4.5 days

Calculating the number of half lives after time has elapsed 27 days:

4.5 days have been elapsed time after 1 half life

So, 27 days must have been elapsed after = \frac{1}{4.5}\times 27=6 half lives

Hence, the number of half lives are 6

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The molar heat of vaporization of water is 40.7kJ/mol. How much heat must be absorbed to convert 50.0 grams of liquid water at 1
EleoNora [17]
During a phase change the temperature does not change since all of the heat is being absorbed in order to break the intermolecular forces.  Due to that, the formula will not need to have T in it and is actually q=nΔH(v).
n=the number of moles (in this case 2.778mol of water since you divide 50g by 18g/mol).
ΔH(v)=the molar heat of vaporization (in this case 40.7kJ/mol).
q=the heat that must be absorbed
q=2.778mol×40.7kJ/mol
q=113.1kJ
Therefore the water needs to absorb 1.13×10²kJ.

I hope this helps.  Let me know if anything is unclear.

4 0
3 years ago
How much copper is in 4.64 grams of copper
Romashka [77]

Answer:

4.64 grams.

Explanation:

without stating a desired unit, stating the answer in any unit is acceptable. So you can use grams and the problem is done for you

6 0
3 years ago
What is the hydronium ion concentration of a 0.100 M acetic acid solution with Ka = 1.8 × 10-5? The equation for the dissociatio
evablogger [386]

Answer:

1.3×10⁻³ M

Explanation:

Hello,

In this case, given the dissociation reaction of acetic acid:

CH_3CO_2H(aq) + H_2O(l) \rightleftharpoons H_3O^+(aq) + CH_3CO_2^-(aq)

We can write the law of mass action for it:

Ka=\frac{[H_3O^+][CH_3CO_2^-]}{[CH_3CO_2H]}

Of course, excluding the water as heterogeneous substances are not included. Then, in terms of the change x due to the dissociation extent, we are able to rewrite it as shown below:

1.8x10^{-5}=\frac{x*x}{0.100-x}

Thus, via the quadratic equation or solve, we obtain the following solutions:

x_1=-0.00135M\\x_2=0.00133M

Obviously, the solution is 0.00133M which match with the hydronium concentration, thus, answer is: 1.3×10⁻³ M in scientific notation.

Regards.

8 0
3 years ago
Read 2 more answers
NaOH+H3PO4=Na3PO4+H20
statuscvo [17]
Wait is that suppose to be a question??!!
4 0
3 years ago
Balance the following reaction.<br> A.) 4<br> B.) 2<br> C.) 5<br> D.) blank<br> E.) 3
slega [8]

Answer:

C.5

Hope this helps

7 0
2 years ago
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