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2 years ago

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A sample of rock contains 80 grams of a parent radioactive isotope that has a half-life of 20 000 years. After 100 000 years, th

e number of grams of the parent radioactive isotope remaining is

1 answer:

Tatiana [17]2 years ago

4 0

Answer:

2.5 g

Explanation:

Number of half lives is 100000/20000 = 5 half lives

so (1/2)^5 = 1/32 of the original sample remains

So (80)(1/32)=2.5 g

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fgiga [73]

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2 years ago

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2 years ago

Calculate the mass of 3.5 mol C6H6

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3 years ago

How many moles are in 7.2x10^15 atoms of Pb?

fiasKO [112]

<h3>Answer:</h3>

1.2 × 10⁻⁸ mol Pb

<h3>General Formulas and Concepts:</h3>

<u>Math</u>

<u>Pre-Algebra</u>

Order of Operations: BPEMDAS

Brackets
Parenthesis
Exponents
Multiplication
Division
Addition
Subtraction

Left to Right<u> </u>

<u>Chemistry</u>

<u>Atomic Structure</u>

Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.

<u>Stoichiometry</u>

Using Dimensional Analysis

<h3>Explanation:</h3>

<u>Step 1: Define</u>

[Given] 7.2 × 10¹⁵ atoms Pb

<u>Step 2: Identify Conversions</u>

Avogadro's Number

<u>Step 3: Convert</u>

[DA] Set up: $\displaystyle 7.2 \cdot 10^{15} \ atoms \ Pb(\frac{1 \ mol \ Pb}{6.022 \cdot 10^{23} \ atoms \ Pb})$
[DA] Multiply/Divide [Cancel out units]: $\displaystyle 1.19562 \cdot 10^{-8} \ mol \ Pb$

<u>Step 4: Check</u>

<em>Follow sig fig rules and round. We are given 2 sig figs.</em>

1.19562 × 10⁻⁸ mol Pb ≈ 1.2 × 10⁻⁸ mol Pb

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2 years ago

Chemistry, please help! Thanks.

Ilya [14]

Answer:

d. The gold(III) ion is most easily reduced.

Explanation:

The standard reduction potentials are

Au³⁺ + 3e⁻ ⟶ Au; 1.50 V

Hg²⁺ + 2e⁻ ⟶ Hg; 0.85 V

Zn²⁺ + 2e⁻ ⟶ Zn; -0.76 V

Na⁺ + e⁻ ⟶ Na; -2.71 V

A <em>more positive voltage</em> means that there is a <em>stronger driving force</em> for the reaction.

Thus, Au³⁺ is the best acceptor of electrons.

Reduction Is Gain of electrons and, Au³⁺ is gaining electrons, so

Au³⁺ is most easily reduced.

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3 years ago