Which of the following chemical formulas shows a covalent bond (a) CO2 (b) MgO (c) NaCL (d) HBr

Lithium, is used in dry cells and storage batteries and in high temperature lubricants, it has two naturally occurring isotopes,

erastovalidia [21]

Answer: The average atomic mass of lithium is 6.9241 u.

Explanation:

Average atomic mass of an element is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

$\text{Average atomic mass }=\sum_{i=1}^n\text{(Atomic mass of an isotopes)}_i\times \text{(Fractional abundance})_i$ ....(1)

For $_3^6\textrm{Li}$ isotope:

Mass of $_3^6\textrm{Li}$ isotope = 6 u

Percentage abundance of $_3^6\textrm{Li}$ isotope = 7.59 %

Fractional abundance of $_3^6\textrm{Li}$ isotope = 0.0759

For $_3^7\textrm{Li}$ isotope:

Mass of $_3^7\textrm{Li}$ isotope = 7 u

Percentage abundance of $_3^7\textrm{Li}$ isotope = 92.41%

Fractional abundance of $_3^7\textrm{Li}$ isotope = 0.9241

Putting values in equation 1, we get:

$\text{Average atomic mass of Lithium}=[(6\times 0.0759)+(7\times 0.9241)]$

$\text{Average atomic mass of Lithium}=6.9241u$

Hence, the average atomic mass of lithium is 6.9241 u.

7 0

3 years ago

What is the oxidation number of cl− in the perchlorate ion

Yuri [45]

Answer:

The answer is: +7

Explanation:

Oxidation state or oxidation number of an element is the hypothetical charge on an element that forms completely ionic bonds. The oxidation number represents the number of electrons lost or gained by that element.

Perchlorate ion is a molecule with a chemical formula: ClO₄⁻

The oxidation state of oxygen in ClO₄⁻ = -2,

the total charge on the ClO₄⁻ molecule = -1,

let the oxidation state of chlorine be x

As the sum of oxidation states of all elements in a molecule is equal to the total charge on the molecule.

⇒ oxidation state of chlorine + oxidation state of oxygen × 4 = total charge on the molecule

⇒ x + (-2) × 4 = -1

⇒ x + (-8) = -1

⇒ x = -1 + 8 = +7

⇒ x = +7

Therefore, the oxidation state of chlorine in the perchlorate ion (ClO₄⁻): x = +7

5 0

3 years ago

Choose the aqueous solution below with the lowest freezing point. These are all solutions of nonvolatile solutes and you should

atroni [7]

Answer:

$(NH_4)_3PO_4$ 0.075 m solution has the lowest freezing point.

Explanation:

Depression in freezing point is given by:

$\Delta T_f=T-T_f$

$\Delta T_f=K_f\times m$

$\Delta T_f=iK_f\times \frac{\text{Mass of solute}}{\text{Molar mass of solute}\times \text{Mass of solvent in Kg}}$

where,

$\Delta T_f$ =Depression in freezing point

$K_f$ = Freezing point constant of solvent

1 - van't Hoff factor

m = molality

According question, molality of all the solutions are same and are in prepared with same solvent. So, values of molality and $K_f$ will remain the same and will not effect the freezing point of the solution.

The lowering in freezing point will now depend upon van't Hoff factors of the solutions. Higher the value of van'Hoff factor more will be the lowering in freezing point of the solution.

The van't Hoff factor of $KNO_2$ solution = $i_1=2$

The van't Hoff factor of $LiCN$ solution = $i_2=2$

The van't Hoff factor of $(NH_4)_3PO_4$ solution = $i_3=4$

The van't Hoff factor of $NaI$ solution = $i_4=2$

The van't Hoff factor of $NaBrO_3$ solution = $i_5=2$

The solution of ammonium phosphate has the highest values of van't Hoff factor which will result in maximum lowering of the freezing point of the solution.

Hence, $(NH_4)_3PO_4$ 0.075 m solution has the lowest freezing point.

4 0

3 years ago

Read 2 more answers

The amount of matter in a given amount of volume is referred to as

Damm [24]

Answer:

It would be Density because:

Density= mass/ volume

Density refers to the amount of matter or mass of a substance over a volume

7 0

3 years ago

Give the name of one or more polysaccharides that matches each of the following descriptions:

adell [148]

Answer:

A Cellulose not digested by humans.

b. the storage form of carbohydrates in plants is starch

C amylose contains 1-4 glycosidic bond

D Glycogen and starch are highly branched polysaccharides.

Explanation:

8 0

2 years ago