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bulgar [2K]
2 years ago
5

Cobalt-60, with a half-life of 5.0 days, is used in cancer radiation treatments. A hospital purchases a 30.0g supply of it and s

tores it on a shelf in a closet. The next time a hospital worker grabs the bottle, though, they find that it only contains 3.75 g remaining! Assuming the bottle had never been opened, how long was the bottle sitting on the shelf before the worked grabbed it?
Chemistry
1 answer:
Rudik [331]2 years ago
8 0

Answer:

Bottle is sitting on the shelf for 15 days.

Explanation:

Given data:

Co-60 half life = 5 days

Total amount = 30.0 g

Amount left = 3.75 g

Time taken = ?

Solution:

AT time zero = 30 g

AT first half life= 30g /2 = 15 g

At 2nd half life = 15 g/ 2 = 7.5 g

At 3rd half life = 7.5 g/2 = 3.75 g

Now we will calculate the sitting time of bottle.

Half life = Time taken / number of half lives

3× 5 days = time taken

Time taken = 15 days

Bottle is sitting on the shelf for 15 days.

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kipiarov [429]

The correct options are these:

1. It will follow the law of conservation of mass.

2.The mass of products will be equal to the mass of the reactants.

The law of conservation of mass states that ' matter can neither be created nor destroyed. Thus, if a chemical equation is balanced, the mass of the reactant at the beginning of the reaction will be equal to the mass of the product after the reaction. This shows that the chemical reaction obeys the law of conservation of mass.

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3 years ago
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Helga [31]
Everything is made out of matter. More specifically atoms.
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Which of the following elements is very reactive and needs to gain one electron to have a full outermost shell?
NISA [10]
Iodine has 7 valence electrons. It needs therefore only 1 electron to be stable this is why it is so reactive.
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3 years ago
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When hydrogen sulfide gas is bubbled into a solution of sodium hydroxide, the reaction forms sodium sulfide and water. How many
Mumz [18]

Answer:

1.61 g Na₂S

Explanation:

To find the mass of sodium sulfide (Na₂S) generated from hydrogen sulfide (H₂S) and sodium hydroxide (NaOH), you need to (1) construct the balanced chemical equation, then (2) calculate the molar masses of each molecule involved, then (3) convert grams of each reagent to grams of the product (via the molar masses and mole-to-mole ratio from equation coefficients), and then (4) determine the limiting reagent and final answer. It is important to arrange the conversions in a way that allows for the cancellation of units (the desired unit should be in the numerator).

(Step 1)

The unbalanced equation:

H₂S + NaOH ---> Na₂S + H₂O

Reactants: 3 hydrogen, 1 sulfur, 1 sodium, 1 oxygen

Products: 2 hydrogen, 1 sulfur, 2 sodium, 1 oxygen

The balanced equation:

H₂S + 2 NaOH ---> Na₂S + 2 H₂O

Reactants: 4 hydrogen, 1 sulfur, 2 sodium 2 oxygen

Products: 4 hydrogen, 1 sulfur, 2 sodium, 4 oxygen

(Step 2)

Molar Mass (H₂S): 2(1.008 g/mol) + 32.065 g/mol

<u>Molar Mass (H₂S)</u>: 34.081 g/mol

Molar Mass (NaOH): 22.990 g/mol + 15.998 g/mol + 1.008 g/mol

<u>Molar Mass (NaOH)</u>: 39.998 g/mol

Molar Mass (Na₂S): 2(22.990 g/mol) + 32.065 g/mol

<u>Molar Mass (Na₂S)</u>: 78.045 g/mol

(Step 3)

1.50 g H₂S          1 mole            1 mole Na₂S          78.045 g
-----------------  x  ----------------  x  --------------------  x  -----------------  =
                           34.081 g          1 mole H₂S            1 mole

=  3.43 g Na₂S

1.65 g NaOH           1 mole              1 mole Na₂S          78.045 g
--------------------  x  ----------------  x  -----------------------  x  ----------------  =
                              39.998 g        2 moles NaOH          1 mole

=  1.61 g Na₂S

(Step 4)

Because NaOH generates less product, it will run out before all of the H₂S is used. This makes NaOH the limiting reagent and the final answer 1.61 grams Na₂S.

5 0
1 year ago
24. As the first five elements in Group 14 are considered in order from top to bottom, there are changes
myrzilka [38]

Answer:

B

Explanation:

As you move down the periodic table in the carbon family, the atomic radius and ionic radius increase while electronegativity and ionization energy decrease. Atom size increases moving down the group because an additional electron shell is added.

8 0
2 years ago
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