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salantis [7]
2 years ago
10

Lanthanum-138 has a half-life of 105 billion years. after 525 billion years, how much of a 240 g sample of this radioisotope wil

l remain? grams
Chemistry
1 answer:
Reika [66]2 years ago
5 0

The amount of the 240 g sample of the radioisotope that will remain after 525 billion years is 7.5 g

<h3>How to the number of half-lives that has elapsed</h3>
  • Half-life (t½) = 105 billion years
  • Time (t) = 525 billion years
  • Number of half-lives (n) = ?

n = t / t½

n = 525 / 105

n = 5

<h3>How to determine the amount remaining</h3>
  • Original amount (N₀) = 240 g
  • Number of half-lives (n) = 5
  • Amount remaining (N) = ?

N = N₀ / 2ⁿ

N = 240 / 2⁵

N = 240 / 32

N = 7.5 g

Learn more about half life:

brainly.com/question/26374513

#SPJ4

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If approximately equal volumes of an acid and a base of equal strengths are combined, the resulting solution should have a pH of
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Answer : The resulting solution will have a pH of 7.

Explanation:

Whenever acid and base reacts with each other to form water molecule is called Neutralization reaction. This water molecules is formed from the  hydronium ion (H^+) from acid and hydroxide ion(OH^-) from base.

When the equal volumes of acid and base of equal strength are combined, the resulting pH of the solution becomes 7.

The pH 7 value means that the solution is neutral.

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3 years ago
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An atom's nucleus has 92 protons and its mass number is 235. how many neutrons are in the nucleus? what is the name of the atom
STALIN [3.7K]
The mass number is the sum of the protons and neutrons in an atom. 235-92 = 143 neutrons.
Element 92 is Uranium.

Uranium is also the highest atomic number element which exists in nature. All of the rest above element 92 only exist nuclear high-energy reactions (the transuranium elements), and most experience nuclear decay very quickly and form other elements with fewer protons. 
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3 years ago
Does CH3F have a higher boiling point than BRF?
Anna71 [15]

Answer:

The boiling point of the fluoromethane (CH3F) is higher than that of fluorine (F2).

7 0
2 years ago
How many grams of hydrochloric acid are produced when 15.0 grams NaCl react with excess H2SO4 in the reaction
e-lub [12.9K]

Answer:

11.65 g

Explanation:

Amount of NaCl  = 15.0 grams

amount of H₂SO₄ = Excess

mass of hydrochloric acid (HCl) = ?

Solution:

To solve this problem first we will look for the reaction that NaCl react with  H₂SO₄

Reaction:

         2NaCl + H₂SO₄ --------> 2 HCl + Na₂SO₄

As the  H₂SO₄ is in excess so the amount of hydrochloric acid (HCl) depends on the amount of NaCl as it its act as limiting reactant.

Now if we look at the reaction

         2NaCl + H₂SO₄ --------> 2HCl + Na₂SO₄

           1 mol                              2 mol  

Now convert moles to mass

Then

Molar mass of NaCl = 23 + 35.5 = 58.5 g/mol

Molar mass of HCl = 1 + 35.5 = 36.5 g/mol

So,

            2NaCl           +      H₂SO₄     -------->       2HCl        +     Na₂SO₄

      2 mol (58.5 g/mol)                                    2 mol (36.5 g/mol)

              94 g                                                           73 g

So if we look at the reaction; 94 g of NaCl gives with 73 g of hydrochloric acid (HCl) in a this reaction, then how many grams of hydrochloric acid (HCl) will produce from 15.0 g of NaCl

For this apply unity formula

           94 g of NaCl  ≅ 73 g of HCl

           15.0 g of NaCl  ≅ X g of HCl

By Doing cross multiplication

           X g of HCl = 73 g x 15.0 g / 94 g

           X g of HCl = 11.65 g

11.65 g of hydrochloric acid (HCl) will produce by 15.0 g of NaCl

7 0
3 years ago
To test paint quality, scientists designed an experiment where the paint was exposed to temperatures ranging from 260 degrees Ce
pishuonlain [190]

Answer:

The independent variable is the temperature to which the paint and materials are exposed

The dependent variable is the presence of peeling and cracking of the paint

The constant rates are the paint and material used for each trial

Explanation:

The treatment the to which the paint is subjected = Temperatures from 260 °C  to 650 °C

The method of determining the paint quality = By peeling and cracking

The types of paint and materials used = The same paint and material

The independent variable is the variable suspected as the cause of the effect being studied. It is the variable introduced as a treatment

In the question, given that the paint is subjected to different temperatures from between 260°C to 650 °C, the temperature changes introduced is the independent variable

Therefore;

The independent variable = The temperature to which the paint and materials are exposed to

The dependent variable is the effect variable. It is the variable of the property being investigated and it is also the variable that is measured in the investigation

In the question, given that the after heating the paint and material, the scientist check for peeling and cracking, the dependent variable is the occurrence of cracking and peeling at a given temperature

Therefore;

The dependent variable = The presence of peeling and cracking of the paint

The constant rate(s) are variables which are kept constant during the investigation, under the different treatments

The constant rate(s) in the tests are the paint and material, which were kept the same for each trial to reduce the effect of underlying factors that may impact on the result and obscure the relationship between the dependent and independent variables

Therefore;

The constant rate are the paint and material used for each trial

8 0
3 years ago
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