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3 years ago

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Chemistry

1 answer:

tatyana61 [14]3 years ago

5 0

Pure metals possess few important physical and metallic properties, such as melting point, boiling point, density, specific gravity, high malleability, ductility, and heat and electrical conductivity. These properties can be modified and enhanced by alloying it with some other metal or nonmetal, according to the need.

Alloys are made to:

Enhance the hardness of a metal: An alloy is harder than its components. Pure metals are generally soft. The hardness of a metal can be enhanced by alloying it with another metal or nonmetal.

Lower the melting point: Pure metals have a high melting point. The melting point lowers when pure metals are alloyed with other metals or nonmetals. This makes the metals easily fusible. This property is utilized to make useful alloys called solders.

Enhance tensile strength: Alloy formation increases the tensile strength of the parent metal.

Enhance corrosion resistance: Alloys are more resistant to corrosion than pure metals. Metals in pure form are chemically reactive and can be easily corroded by the surrounding atmospheric gases and moisture. Alloying a metal increases the inertness of the metal, which, in turn, increases corrosion resistance.

Modify color: The color of pure metal can be modified by alloying it with other metals or nonmetals containing suitable color pigments.

Provide better castability: One of the most essential requirements of getting good castings is the expansion of the metal on solidification. Pure molten metals undergo contraction on solidification. Metals need to be alloyed to obtain good castings because alloys

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The ammonia molecule in the diagram has the observed bond orientation because ...

aivan3 [116]

Answer:

Nitrogen has four pairs of electrons: 3 bonds and 1 lone pair in the valence shell;
Electrons repel one another based on the VSEPR theory;
Nitrogen has a total of 7 protons (its atomic number is 7) in its nucleus.

Explanation:

The shape and the bond orientation of molecules and ions are both explained by the valences shell electron pair repulsion theory (VSEPR).

Ammonia, $NH_3$ , is a molecule which contains three N-H bonds, as well as one lone pair on nitrogen. According to the VSEPR theory, molecules try to acquire a shape which would minimize the repulsion exhibited by the electron clouds present, that is, between the bonding (shared in a bond) and non-bonding (lone pair) electrons.

In VSEPR, our main step is to calculate the steric number, this is the sum of the number of bonds (ignoring the multiplicity of any bond) and the lone pairs on a central atom. In ammonia, we have 3 bonds and 1 lone pair, totaling to a steric number of 4. A steric number of 4 without any lone pairs on a central atom and just bonds would yield a tetrahedral shape with bond angles of $109.5^o$ .

Now, in this case, since we have a lone pair instead of a bond, it is repelling stronger decreasing the bond angles to about $107^o$ .

The greater the number of lone pairs, the lower the angle becomes.

To summarize:

Nitrogen has four pairs of electrons: 3 bonds and 1 lone pair in the valence shell;
Electrons repel one another based on the VSEPR theory;
Nitrogen has a total of 7 protons (its atomic number is 7) in its nucleus.

3 0

3 years ago

If water were a non-polar<br> Molecule

JulijaS [17]

Answer:

Water would not be able to transport nutrients -‐-‐ in plants, or in our bodies -‐-‐ nor to dissolve and transport waste products out of our bodies. ... Cohesiveness, adhesiveness, and surface tension: would decrease because without the +/-‐ polarity, water would not form hydrogen bonds between H20 molecules.

8 0

3 years ago

What is the name of the molecule below?

SIZIF [17.4K]

Answer:

C.) 2-butyne

Explanation:

Since the molecule has 4 central carbons, it has the prefix but-.

Since the molecule has a triple bond between central carbons, it has an ending of -yne.

Since the triple bond starts on the second carbon, it has a 2 - prefix.

3 0

3 years ago

The density of H2O2 is 1.407 g/mL, and the density of O2 is 1.428 g/L. How many liters of O2 can be made from 55 mL H2O2

balandron [24]

Explanation:

mass H2O2 = 55 mL(1.407 g/mL) = 80.85 g

molar mass H2O2 = 2(1.01 g/mol) + 2(16.00 g/mol) = 34.02 g/mol

moles H2O2 = 80.85 g/34.02 g/mol = 2.377 moles H2O2

For each mole of H2O2 you obtain 0.5 mole of O2 (see the equation).

moles O2 = 2.377 moles H2O2 (1 mole O2)/(2 moles H2O2) = 1.188 moles O2

Now, you need the temperature. If you are at STP (273 K, and 1.00 atm) then 1 mole of an ideal gas at STP has a volume of 22.4 L. Without temperature you are not really able to continue. I will assume you are at STP.

Volume O2 = 1.188 moles O2(22.4 L/mole) = 0.0530 L of O2.

which is 53 mL.

8 0

2 years ago

What are some benefits that come from volcanoes?

nataly862011 [7]

Answer:

Volcanoes cool off the earth by emitting heat from its interior. They also add islands and for example, Hawaii was created / is made out of volcanoes. The deposits from volcanoes can also be used for building materials. Volcanic explosions have caused the atmosphere and oceans to form. Volcanic deposits also create land which is fertile.

7 0

3 years ago

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