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3 years ago

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Calculate the molecular mass or formula mass (in amu) of each of the following substances: (a) BrN3 amu (b) C2H6 amu (c) NF2 amu

(d) Al2S3 amu (e) Fe(NO3)3 amu (f) Mg3N2 amu (g) (NH4)2CO3 amu

2 answers:

hram777 [196]3 years ago

6 0

Answer:

Explanation:

The atomic unit of mass (a.m.u) is the unit used to compare the relative masses of atoms. An atomic mass unit is a twelfth of the mass of a carbon-12 atom.

The calculation of the molecular mass of a compound is done by adding the relative atomic masses of the atoms of the formula of said substance, taking into account its abundance in the compound. The atomic mass of the atoms that make up the molecule are obtained in the Periodic Table.

So, in these cases you have:

<u><em>BrN₃:</em></u>

You know the atomic masses of the elements that make up the molecule, obtained from the periodic table:

Br: 79.9 amu

N: 14 amu

I take into account the abundance of each element in the compound you get:

<em><u>BrN₃=79.9 amu + 3* 14 amu= 121.9 amu</u></em>

<u><em>C₂H₆:</em></u>

You know the atomic masses of the elements that make up the molecule, obtained from the periodic table:

C: 12 amu

H: 1 amu

I take into account the abundance of each element in the compound you get:

<u><em>C₂H₆= 2*12 amu + 6*1 amu= 30 amu</em></u>

<u><em>NF₂:</em></u>

You know the atomic masses of the elements that make up the molecule, obtained from the periodic table:

N: 14 amu

F: 19 amu

I take into account the abundance of each element in the compound you get:

<em><u>NF₂= 14 amu + 2*19 amu= 52 amu</u></em>

<u><em>Al₂S₃:</em></u>

You know the atomic masses of the elements that make up the molecule, obtained from the periodic table:

Al: 27 amu

S: 32 amu

I take into account the abundance of each element in the compound you get:

<em><u>Al₂S₃= 2*27 amu + 3*32 amu= 150 amu</u></em>

<u><em>Fe(NO₃)₃:</em></u>

<u><em> </em></u>You know the atomic masses of the elements that make up the molecule, obtained from the periodic table:

Fe: 55.85 amu

N: 14 amu

O: 16 amu

I take into account the abundance of each element in the compound you get:

Fe(NO₃)₃= 55.85 amu + 3*(14 amu + 3*16 amu)= 241.85 amu

<u><em>Mg₃N₂:</em></u>

You know the atomic masses of the elements that make up the molecule, obtained from the periodic table:

N: 14 amu

Mg: 24 amu

I take into account the abundance of each element in the compound you get:

<u><em>Mg₃N₂= 3*24 amu + 2*14 amu= 100 amu</em></u>

<u><em>(NH₄)₂CO₃:</em></u>

You know the atomic masses of the elements that make up the molecule, obtained from the periodic table:

N: 14 amu

H: 1 amu

C: 12 amu

O: 16 amu

I take into account the abundance of each element in the compound you get:

<em><u>(NH₄)₂CO₃: 2*(14 amu + 4*1 amu) + 12 amu+3*16 amu= 96 amu</u></em>

irakobra [83]3 years ago

5 0

Answer:

Shown below

Explanation:

a) for BrN3

80+3(14)=122amu

b) forC2H6

2(12) + 6(1) = 30amu

C) for NF2

14+2(19) = 52amu

D) Al2S3

2(27) + 3(32)= 150amu

E) for Fe(NO3)3

56 + 3 [14+3(16)] =242amu

F) Mg3N2

3(24) + 2(14)= 100amu

G) for (NH4)2CO3

2[14 +4(1)] +12 +3(16)=96amu

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Answer: The theoretical yield of aspirin is 4.14 g

Explanation:

To calculate the moles :

$\text{Moles of solute}=\frac{\text{given mass}}{\text{Molar Mass}}$ $\text{Moles of salicylic acid}=\frac{3.20g}{138.12g/mol}=0.023moles$

mass of acetic anhydride = $density\times volume =1.082g/ml\times 3.71ml=4.01g$

$\text{Moles of acetic anhydride}=\frac{4.01g}{102.04g/mol}=0.039moles$

$C_9H_6O_3+C_4H_6O_3\rightarrow C_9H_8O_4+C_2H_3O_2$

According to stoichiometry :

1 mole of salycylic acid require 1 mole of acetic anhydride

Thus 0.023 moles of salycylic acid require= $\frac{1}{1}\times 0.023=0.023moles$ of acetic anhydride

Thus salycylic acid is the limiting reagent as it limits the formation of product and acetic anhydride is the excess reagent.

As 1 mole of salycylic give = 1 mole of aspirin

Thus 0.023 moles of salycylic acid give = $\frac{1}{1}\times 0.023=0.023moles$ of aspirin

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In other words, each stable isotope will contribute to the average mass of the element proportionally to its abundance.

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Answer:

The molecular weight is $Z = 111.2 \ g/mol$

Explanation:

From the question we are told that

The mass of the sample is $m = 0.98 \ g$

The temperature is $T = 348 K$

The volume which the gas occupied is $V = 265 \ ml = 265 *10^{-3} L$

The pressure is $P = 0.95 \ atm$

Generally from the ideal gas equation we have that

$PV = n RT$

Here n is the number of moles of the gas while the R is the gas constant with value $R = 0.0821 \ atm \cdot L \cdot mol^{-1} \cdot K^{-1}$

$n = \frac{PV}{ RT}$

=> $n = \frac{ 0.95 * 265 *10^{-3} }{ 0.0821 * 348}$

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Generally the molecular weight is mathematically represented as

$Z = \frac{m}{n}$

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<em>Metals (Sodium , potassium , calcium , gold are solid)</em>

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