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3 years ago

5

A sample of neon effuses from a container in 76 seconds. the same amount of an unknown noble gas requires 155 seconds. part a id

entify the gas.

2 answers:

Karolina [17]3 years ago

6 0

The rate of gas effusion or diffusion is inversely proportional to the square root of molar mass
molar mass of neon is 20
let the molar mass of unknown gas be y
155/76=sqrs of y/20
square both side to remove the square root sign
155^2/76^2 =y/20
by cross multiplication y={(24025 x 20)/5776}=83.18

the gas is krypton since 83 is one isotope of krypton

Deffense [45]3 years ago

3 0

Answer: The other gas is Krypton (Kr).

Explanation: The rate of effusion of gas is given by Graham's Law.

Graham's Law states that the rate of effusion of gas is inversely proportional to the square root of their atomic masses.

Mathematically,

$\text{Rate of effusion}=\frac{1}{\sqrt{\text{Molar mass}}}$

Rate of effusion is the amount of gas effused in a given time 't'

Mathematically,

$\text{Rate of effusion}=\frac{V}{t}$

As per the question:

For Neon:

$t_1=76sec\\M_1=20$

For unknown gas:

$t_2=155sec\\M_2=?$

$V_{neon}=V_{\text{unknown gas}}$

Putting values in rate of effusion formula, we get:

$\frac{\frac{V_{neon}}{t_1}}{\frac{V_{\text{unknown gas}}}{t_2}}=\sqrt{\frac{M_2}{M_1}}$

$\frac{155}{76}=\sqrt{\frac{M_2}{20}}$

$M_2=83.150$

This mass corresponds to the mass of Krypton noble gas.

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How many molecules are in 3.6 grams of NaCl? Question options:

Levart [38]

Answer:

$\boxed {\boxed {\sf 3.7 * 10^{22} \ molecules \ NaCl}}$

Explanation:

We are asked to find how many molecules are in 3.6 grams of sodium chloride.

<h3>1. Convert Grams to Moles </h3>

First, we convert grams to moles using the molar mass. These values are equivalent to atomic masses on the Periodic Table, but the units are grams per moles instead of atomic mass units. Look up the molar masses of the individual elements: sodium and chlorine.

Na: 22.9897693 g/mol
Cl: 35.45 g/mol

There are no subscripts in the chemical formula (NaCl), so we simply add the 2 molar masses.

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Now we will convert using dimensional analysis. First, set up a ratio using the molar mass.

$\frac {58.4397693 \ g \ NaCl}{ 1 \ mol \ NaCl}$

We are converting 3.6 grams to moles, so we must multiply the ratio by this value.

$3.6 \ g \ NaCl *\frac {58.4397693 \ g \ NaCl}{ 1 \ mol \ NaCl}$

Flip the ratio so the units of grams of sodium chloride cancel.

$3.6 \ g \ NaCl *\frac { 1 \ mol \ NaCl}{58.4397693 \ g \ NaCl}$

$3.6 *\frac { 1 \ mol \ NaCl}{58.4397693}$

$\frac { 3.6}{58.4397693} \ mol \ NaCl$

$0.06160188589 \ mol \ NaCl$

<h3>2. Convert Moles to Molecules </h3>

Next, we convert moles to molecules using Avogadro's Number. This is 6.022 × 10²³ and it tells us the number of particles (atoms, molecules, formula units, etc). In this case, the particles are molecules of sodium chloride. Let's set up another ratio.

$\frac {6.022 \times 10^{23} \ molecules \ NaCl}{ 1 \ mol \ NaCl}$

Multiply by the number of moles we calculated.

$0.06160188589 \ mol \ NaCl * \frac{6.022 \times 10^{23} \ molecules \ NaCl}{1 \ mol \ NaCl}$

The units of moles of sodium chloride cancel.

$0.06160188589 * \frac{6.022 \times 10^{23} \ molecules \ NaCl}{1 }$

$3.70966557*10^{22} \ molecules \ NaCl$

<h3>3. Round </h3>

The original measurement of grams (3.6) has 2 significant figures, so our answer must have the same. For the number we found, that is the tenths place. The 0 in the hundredth place tells us to leave the 7 in the tenth place.

$3.7 * 10^{22} \ molecules \ NaCl$

There are $3.7 * 10^{22} \ molecules \ NaCl$ in 3.6 grams and the correct answer is choice D.

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3 years ago