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3 years ago

What is the mass of 1.20 x 10^25 atoms of He

Chemistry

1 answer:

AleksandrR [38]3 years ago

4 0

Answer:

79.7 g He

General Formulas and Concepts:

Chemistry - Atomic Structure

Reading a Periodic Table
Using Dimensional Analysis
Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.

Explanation:

Step 1: Define

1.20 × 10²⁵ atoms He

Step 2: Identify Conversions

Avogadro's Number

Molar Mass of He - 4.00 g/mol

Step 3: Convert

$1.20 \cdot 10^{25} \ atoms \ He(\frac{1 \ mol \ He}{6.022 \cdot 10^{23} \ atoms \ He} )(\frac{4.00 \ g \ He}{1 \ mol \ He} )$ = 79.7077 g He

Step 4: Check

We are given 3 sig figs. Follow sig fig rules and round.

79.7077 g He ≈ 79.7 g He

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Explanation:

From Arrhenius equation

$K=Ae^{\frac{E_{a} }{RT} }$

where; K = Rate of constant

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taking logarithm on both sides of the equation we have;

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since we have the rate of two different temperature the equation can be derived as:

$In(\frac{K_{2} }{K_{1} } )=\frac{E_{a} }{R}(\frac{1}{T_{1} } -\frac{1}{T_{2} } )$

$In(\frac{K_{2} }{K_{1} } )=\frac{165000J/mol}{8.314JK^{-1}mol^{-1} }.(\frac{1}{505} -\frac{1}{525} )$

$In(\frac{K_{2} }{K_{1} } )$ = 19846.04×7.544× $10^{-5}$ = 1.497

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