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Leokris [45]
3 years ago
13

Boron has an atomic mass of 10.8 amu. It is known that naturally occurring boron is composed of two isotopes, boron-10 and boron

-11. Determine the percent of each isotope of boron

Chemistry
2 answers:
ANEK [815]3 years ago
8 0
B-10 = 19.9%
B-11 = 80.1%

Abundance of B10 = x
Abundance of B11= y
You know x+y = 1 because there are only the 2 isotopes.
Y= 1-x

10.01294x + 11.00931 (1-x) = 10.811
10.01294x + 11.00931 - 11.00931x = 10.811 - 0.99016x = -0.198
X = 0.200

Check:
10.01294(0.2) + 11.00931 (0.8) = 10.81

20% B10. 80% B11
Finger [1]3 years ago
7 0

Answer: Boron -10 : 20%

Boron -11 : 80%

Explanation:

Mass of isotope  boron -10= 10

% abundance of isotope 1 = x% = \frac{x}{100}

Mass of isotope boron-11 = 11

% abundance of isotope 2 = (100-x)% = \frac{100-x}{100}

Formula used for average atomic mass of an element :

\text{ Average atomic mass of an element}=\sum(\text{atomic mass of an isotopes}\times {{\text { fractional abundance}})

10.8=\sum[(10)\times \frac{x}{100})+(11)\times \frac{100-x}{100}]]

x=20

Therefore, percent of boron -10 is 20% and isotope boron-11 is (100-20)= 80%.

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Answer:

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Explanation:

We want to convert from moles of water to grams of water.

First, find the molar mass of water (H₂O) Look on the Periodic Table for the masses of hydrogen and oxygen.

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  • Oxygen (O): 15.999 g/mol

Next, add up the number of each element in water. The subscript of 2 comes after the H, so there are 2 moles of hydrogen.

  • 2 Hydrogen: (1.008 g/mol*2) = 2.016 g/mol

Finally, add the molar mass of 2 hydrogen and 1 oxygen.

  • 2.016 g/mol (2 Hydrogen) + 15.999 g/mol (1 oxygen)= 18.015 g/mol

Next, find the grams in 6.5 moles.

Use the molar mass we just found as a ratio.

molar \ mass \ ratio: \frac{18.015 \ g \ H_2O}{1 \ mol \ H_2O}

We want to find the grams in 6.5 moles. We can multiply the ratio above by 6.5

6.5 \ mol \ H_2O * \frac{18.015 \ g \ H_2O}{1 \ mol \ H_2O}

Multiply. Note that the moles of H₂O will cancel each other out.

6.5 * \frac{18.015 \ g \ H_2O}{1}

6.5 * {18.015 \ g \ H_2O}

117.0975 \ g \ H_2O

If we want to round to the technically correct significant figures, it would be 2 sig figs. The original measurement, 6.5, has 2 (6 and 5).

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Which statement defines the temperature of a sample of matter?
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Butane is a member of the CnH2n+2 homologous series is an alkane. Alkanes have C-H and C-C bonds which have Van der waals dispersion forces which are temporary dipole-dipole forces (forces caused by the electron movement in a corner of the atom). This bond is weak but increases as the carbon chain/molecule increases.

In Propan-1-ol(Primaryalcohol), there is a hydrogen bond present in the -OH group. Hydrogen bond is caused by the attraction of hydrogen to a highly electronegative element like Cl-, O- etc. This bond is stronger than dispersion forces because of the relative energy required to break the hydrogen bond. Alcohols (CnH2n+1OH) also experience van der waals dispersion forces on its C-C chain and C-H so as the Carbon chain increases the boiling point increases in the homologous series.

Propanal which is an Aldehyde (Alkanal) with the general formula CnH2n+1CHO. This molecule has a C-O, C-C and C-H bonds only. If you notice, the Oxygen is not bonded to the Hydrogen so there is no hydrogen bond but the C-O bond has a permanent dipole-dipole force caused by the electronegativity of oxygen which is bonded to carbon. It also has van der waals dispersion forces caused by the C-C and C-H as the carbon chain increases down the homologous series. The permanent dipole-dipole forces are not as easy to break as van der waals forces.

In conclusion, the hydrogen bonds present in alcohols are stronger than the permanent dipole-dipole bonds in the aldehyde and the van der waals forces in alkanes (irrespective of the carbon chain in Butane). So Butane < Propanal < Propan-1-ol

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