CHEMISTRY HIGH SCHOOL

Which element has the greatest density at STP?(1) scandium (3) silicon
(2) selenium (4) sodium

Answers

Answer 1

Answer:

Selenium has the greatest density at STP.

Explanation:

According to Ideal gas equation,

P V = n R T

where;

n = m/M

Therefore,

P V = m R T / M

Rearranging,

P M = (m/V) R T

Also,

m/V = density = d

So,

P M = d R T

Solving for density,

d = P M / R T

According to this equation density is directly proportional to Molar mass of a substance. Hence, the Atomic masses of given compounds are listed below,

Scandium = 44.96 g.mol⁻¹

Selenium = 78.97 g.mol⁻¹

Silicon = 28.09 g.mol⁻¹

Sodium = 22.99 g.mol⁻¹

Therefore, selenium having the greatest Atomic Mass will have the greatest density. The densities of given elements are as follow;

Scandium = 2.98 g.cm⁻³

Selenium = 4.81 g.cm⁻³

Silicon = 2.33 g.cm⁻³

Sodium = 0.96 g.cm⁻³

Answer 2

Answer:

$\boxed{\left( 2 \right){\text{ Selenium}}}$ has the greatest density at STP.

Further Explanation:

Ideal gas law is the equation of state for any hypothetical gas. The expression for the ideal gas equation is as follows:

${\text{PV}} = {\text{nRT}}$ …… (1)

Here,

P is the pressure.

V is the volume.

T is the absolute temperature.

n is the number of moles.

R is the universal gas constant.

The formula to calculate the number of moles is as follows:

${\text{n}}=\frac{{\text{m}}}{{\text{M}}}$ ...... (2)

Here,

n is the number of moles.

m is the mass.

M is the molar mass.

Substitute the value of n from equation (2) in equation (1).

${\text{PV}} = \frac{{{\text{mRT}}}}{{\text{M}}}$ …… (3)

Rearrange equation (3) as follows:

${\text{PM}} = \frac{{{\text{mRT}}}}{{\text{V}}}$ …… (4)

The formula to calculate density is as follows:

${\rho }} = \frac{{\text{m}}}{{\text{V}}}$ ...... (5)

Here,

${\rho }}$ is the density.

m is the mass.

V is the volume.

Substitute equation (5) in equation (4).

${\text{PM}} = \rho{\text{RT}}$ …… (6)

Rearrange equation (6) to calculate the density.

${\rho }} = \frac{{{\text{PM}}}}{{{\text{RT}}}}$ ...... (7)

At STP, T and P remain constant, R is already a constant. So according to equation (7), density of substance is directly proportional to the molar mass of the substance.

The molar mass of scandium is 44.96 g/mol.

The molar mass of selenium is 78.97 g/mol.

The molar mass of silicon is 28.09 g/mol.

The molar mass of sodium is 22.99 g/mol.

The molar mass of selenium is the highest among the given elements so its density will be the greatest.

Learn more:

1. Which statement is true for Boyle’s law: brainly.com/question/1158880

2. Calculation of volume of gas: brainly.com/question/3636135

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Ideal gas equation

Keywords: P, V, n, R, T, ideal gas, pressure, volume, selenium, sodium, scandium, silicon, 22.99 g/mol, 78.97 g/mol, 28.09 g/mol, 44.96 g/mol, density, molar mass.

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Answers

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Answers

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brainly.com/question/32037662

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Answers

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Answers

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