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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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Compare a mixture and a compound. How are they alike?
harina [27]

Answer:

1.Difference.

Mixtures are physically combined and can be separated by physical means while compounds are chemically combined and are separated by chemical means.

2.Mixtures do not have mixed boiling and melting points while compounds have mixed boiling and melting points.

2.Similarity.

Both mixtures and compounds are composed of two or more substances or elements combined.

Both can be separated.

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3 years ago
What is represented at the triple point of water?
Aleks04 [339]

Answer:D

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3 years ago
If you start with 13 mole H2O and 50 grams of O2 what is the percent yield of H202 if 100 grams of H202 is actually made?
dmitriy555 [2]

Answer:

94.1 %

Explanation:

We firstly determine the equation:

2H₂O + O₂ →  2H₂O₂

2 moles of water react to 1 mol of oxygen in order to produce 2 moles of oxygen peroxide.

We convert the mass of oxygen to moles:50 g . 1mol /32g = 1.56 mol

Certainly oxygen is the limiting reactant.

2 moles of water react to 1 mol of oxygen.

13 moles of water may react to 13/2 = 6.5 moles. (And we only have 1.56)

As we determine the limiting reactant we continue to the products:

1 mol of O₂ can produce 2 moles of H₂O₂

Then 1.56 moles of O₂ will produce (1.56 . 2) = 3.125 moles

We convert the moles to mass: 3.125 mol . 34 g/mol= 106.25 g

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Percent yield = (Yield produced / Theoretical yield) . 100

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3 0
3 years ago
Question 1(Multiple Choice Worth 3 points)
NNADVOKAT [17]
<h3><u>Answer;</u></h3>

= 3.064 g/L

<h3><u>Explanation;</u></h3>

Using the equation;

PV = nRT , where P is the pressure,. V is the volume, n is the number of moles and T is the temperature and R is the gas constant, 0.08206 L. atm. mol−1.

Number of moles is 1 since one mole has a mass equivalent to the molar mass.

Therefore; We can find the volume and thus get the density.

V = nRT/P

   = (1 × 0.08206 × 498 )/ 0.939

   = 43.52 L

But; density = mass/volume

Therefore;

Density = 133.34 / 43.52

             = 3.064 g/L

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