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bagirrra123 [75]
3 years ago
11

A sample initially contained 150 mg of radon-222. After 11.4 days only 18.75mg of the radon-222 in the sample remained. How many

half lived have passed?
Chemistry
1 answer:
beks73 [17]3 years ago
7 0

<u>Answer: </u>

A sample initially contained 150 mg of radon-222. After 11.4 days only 18.75mg of the radon-222 in the sample remained where 3 half-lives have passed

<u>Explanation:</u>

Given, the initial value of the sample, A_0 = 150mg

Final value of the sample or the quantity left, A = 18.75mg

Time = 11.4 days

The amount left after first half life will be ½.

The number of half-life is calculated by the formula

\frac{A}{A_{0}}=\left(\frac{1}{2}\right)^{N}

where N is the no. of half life

Substituting the values,

\frac{18.75}{150}=\left(\frac{1}{2}\right)^{N}

\left(\frac{1}{2}\right)^{3}=\left(\frac{1}{2}\right)^{N}

On equating, we get, N = 3

Therefore, 3 half-lives have passed.

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Answer:

The entropy of the final solution decreases, as the reaction disorder is less.

Explanation:

The higher the temperature, the greater the heat of the reaction and the greater the disorder it has, so the entropy will increase ... But this is not the case, since the solution cools, decreasing the entropy proportionally.

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3 years ago
Sodium hydroxide (NaOH) and hydrochloric acid (HCl) combine to make table salt (NaCl) and water (H2O). Which equation is balance
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The equation that is balanced among the given options is the first equation NaOH + HCl → NaCl + H2O

From the question,

We are to determine which of the options gives a balanced equation for the reaction between sodium hydroxide (NaOH) and hydrochloric acid (HCl) to make table salt (NaCl) and water (H₂O)

To do this, we will check which of the given equations is balanced, by checking the equations one after the other.

First, we will define what is meant by balanced equation.

Balanced equations are those whose coefficients result in equal numbers of atoms for each element in the reactants and products

  • For NaOH + HCl → NaCl + H2O

On the reactants side

Na = 1

O = 1

H = 2

Cl = 1

On the products side

Na = 1

O = 1

H = 2

Cl = 1

Since equal number of atoms of each element are present at both the reactants and products sides, then the equation is balanced

  • For 2NaOH + 2HCl → 2NaCl + H2O

On the reactants side

Na = 2

O = 2

H = 4

Cl = 1

On the products side

Na = 2

O = 1

H = 2

Cl = 2

The number of atoms of each element present at the reactants side and that present at products side are not equal.

∴ The equation is not balanced

  • For 2NaOH + HCl → NaCl + H2O

On the reactants side

Na = 2

O = 2

H = 3

Cl = 1

On the products side

Na = 1

O = 1

H = 2

Cl = 1

The number of atoms of each element present at the reactants side and that present at products side are not equal.

∴ The equation is not balanced

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On the reactants side

Na = 1

O = 1

H = 2

Cl = 2

On the products side

Na = 1

O = 1

H = 2

Cl = 1

The number of atoms of each element present at the reactants side and that present at products side are not equal.

∴ The equation is not balanced

Hence, the equation that is balanced is the first equation NaOH + HCl → NaCl + H2O

Learn more here: brainly.com/question/17015942

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