Chemistry, 08.07.2019 01:30 Tcutety

Calculate the number of moles of bromine present in 20.5 ml of br2(l), whose density is 3.12 g/ml.

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Answer from: esmeralda266

The 20.5 ml of bromine sample has been consisted of 0.4 mol.

Density can be defined as the mass of an element per unit volume. The density (D) can be expressed as:

$D=\dfrac{M}{V}$

Where, m has been the mass of the compound

V has been the volume of the compound.

The given Bromine has:

$D=3.12\;\text {g/ml}\\V=20.5\;\rm ml$

The mass of bromine has been calculated by substituting the values as:

$3.12=\dfrac{m}{20.5}\\\\m=3.12\;\times\;20.5\;\text g\\\\m=63.96\;\text g$

The mass of bromine sample has been 63.96 g. The moles of the sample has been calculated as:

$M=\dfrac{m}{mwt}$

Where, mass of the substance, $m=63.96\;\text g$

Molecular weight of the substance, $mwt=159.81\;\text{g/mol}$

Substituting the values for calculating moles (M) as:

$M=\dfrac{63.96}{159.81}\;\text{mol}\\\\M= 0.4\;\text{mol}$

The number of moles of $\rm Br_2$ present in 20.5 ml has been 0.4 mol.

For more information about density, refer to the link:

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Answer from: miguelelmenor910

There are 0.400 mol Br₂ in the sample..

Mass of Br₂ = 20.5 mL Br₂ × 3.12 g Br₂/1 mL Br₂ = 63.96 g Br₂.

Moles of Br₂ = 63.96 g Br₂ × (1 mol Br₂/159.81 mol Br₂) = 0.400 mol Br₂

Answer from: Quest

The correct answer is c

Answer from: Quest

assuming that your periodic table has eighteen columns, you should highlight the four elements in the third column from the left of the table.

explanation

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the $3d$ have energy higher than those in the $4 s$ orbital while lower than those of the $4 p$ orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the $4s$ orbital is therefore filled right after $3p$ orbitals and before $3 d$ orbitals.

potassium has electron configuration $[\text{ar}] 4 s^{1}$ and calcium $[\text{ar}] 4 s^{2}$ . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration $[\text{ar}] 4 s^{2} \; 3d^{1}$ and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the $ns^{2} \; (n-1) p^{1}$ and should be highlighted as well.

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Calculate the number of moles of bromine present in 20.5 ml of br2(l), whose density is 3.12 g/ml....

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