10 Points

1.As per the Aufbau principle, which of the following orbitals have the lowest energy?

madam [21]

The correct answer attached in file, Thank you for joining brainly community.

3 0

2 years ago

Boron has two isotopes, Boron 10 which has a mass of 10.0129 amu and Boron-11 with a mass of 11.0093 amu. B-10 occurs 84.74% of

podryga [215]

The average atomic mass of Boron: 10.431 amu

<h3>Further explanation </h3>

Isotopes are atoms whose no-atom has the same number of protons while still having a different number of neutrons.

So Isotopes are elements that have the same Atomic Number (Proton)

Atomic mass is the average atomic mass of all its isotopes

In determining the mass of an atom, as a standard is the mass of 1 carbon-12 atom whose mass is 12 amu

Mass atom X = mass isotope 1 . % + mass isotope 2.% + ...

The average atomic mass of boron :

$\tt avg~mass=0.8474\times 10.0129+0.1526\times 11.0093\\\\avg~mass=10.431~amu$

3 0

3 years ago

How many particles are present in 12.47 grams of NaCl

liq [111]

Answer:

1.26*10²³ particles are present in 12.47 grams of NaCl

Explanation:

Avogadro's Number or Avogadro's Constant is called the number of particles that make up a substance (usually atoms or molecules) and that can be found in the amount of one mole of said substance. Its value is 6.023 * 10²³ particles per mole. The Avogadro number applies to any substance.

So, first of all you must know the amount of moles that represent 12.47 grams of NaCl. For that it is necessary to know the molar mass.

You know:

Na: 23 g/mole
Cl: 35.45 g/mole

So the molar mass of NaCl is: 23 g/mole + 35.45 g/mole= 58.45 g/mole

Now you apply a rule of three as follows: if 58.45 grams are present in 1 mole of NaCl, 12.47 grams in how many moles will they be?

$moles=\frac{12.47 grams*1 mole}{58.45 grams}$

moles= 0.21

You apply a rule of three again, knowing Avogadro's number: if in 1 mole of NaCl there are 6,023 * 10²³ particles, in 0.21 moles how many particles are there?

$number of particles=\frac{0.21 moles*6.023*10^{23} }{1 mole}$

number of particles= 1.26*10²³

1.26*10²³ particles are present in 12.47 grams of NaCl

5 0

3 years ago

NAME the four phases of matter and DESCRIBE how the intermolecular forces and kinetic energy change as you change phases.

weqwewe [10]

Answer: Substances on Earth can exist in one of four phases, but mostly, they exist in one of three: solid, liquid or gas. Learn the six changes of phase: freezing, melting, condensation, vaporization, sublimation and deposition. Intermolecular forces are forces between molecules that determine the physical properties of liquids and solids. 11.2 Vaporization and Vapor Pressure— vaporization is the conversion of a liquid to a gas (vapor), and the quantity of heat associated with this phase change is known as the enthalpy (heat) of vaporization. When kinetic energy is increasing molecules are simply moving faster. However, when the potential energy is increasing molecules are changing phases. Therefore, when the potential energy is increasing is when the molecule is changing phases. Phase changes require either the addition of heat energy (melting, evaporation, and sublimation) or subtraction of heat energy (condensation and freezing). ... Changing the amount of heat energy usually causes a temperature change.

HOpe this helps..... Stay safe and have a Merry Christmas!!!!!!!!!! :D

5 0

2 years ago

Calculate the vapor pressure of a solution made by dissolving 109 grams of glucose (molar mass = 180.2 g/mol in 920.0 ml of wate

Fynjy0 [20]

Given data: molar mass = 180.2 g/mol in 920.0 ml of water at 25 °c.
the vapor pressure of pure water at 25 °c is 23.76 mm hg.
Asked: the vapor pressure of a solution made by dissolving 109 grams of glucose

Solution:
moles glucose = 109 g/ 180.2 g/mol=0.605
mass water = 920 mL x 1 g/mL = 920 g
moles water = 920 g/ 18.02 g/mol=51.1
mole fraction water = 51.1 / 51.1 + 0.605 =0.988
vapor pressure solution = 0.988 x 23.76 = 23.47 mm Hg

6 0

3 years ago