Which of the following is the correct definition of density?

What is common about the elements of a period? Select all that apply. They have the same number of electron energy levels. They

Flauer [41]

A period is the horizontal row of elements in the periodic table and they are numbered from one to seven. In the same period, atomic number increases from left to right. Elements in the same period have the same number of electron energy levels and they transition from a metal to noble gas.

8 0

3 years ago

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Who described the atom as being like plum pudding?

matrenka [14]

Answer:

B

Explanation:

J.J. Thomson

The plum pudding model is an early 20th century model of an atom. It was later found to be wrong. It was proposed by J.J. Thomson in 1904, after the electron had been discovered, but before the atomic nucleus was discovered.

7 0

4 years ago

A 100-watt light bulb radiates energy at a rate of 100 J/s. (The watt, a unit of power or energy over time, is defined as 1 J/s

Maslowich

Answer:

Approximately $2.64\times 10^{20}$ (assumption: wavelength $525\; \rm nm$ is measured in vacuum, where the speed of light is approximately $3.0\times 10^{8}\; \rm m \cdot s^{-1}$ .)

Explanation:

Convert the unit of wavelength to meters:

$\displaystyle \lambda = 525\; \rm nm = 525 \; \rm nm\times \frac{10^{-9}\; \rm m}{1\; \rm nm} = 5.25 \times 10^{-7}\; \rm m$ .

Assume that the wavelength $525\; \rm nm$ is measured in vacuum, where the speed of light is approximately $2.99792\times 10^{8}\; \rm m \cdot s^{-1}$ . Calculate the frequency of this light from its wavelength:

$\displaystyle f = \frac{c}{\lambda} \approx \frac{2.99792\times 10^{8}\; \rm m \cdot s^{-1}}{5.25 \times 10^{-7}\; \rm m} \approx 5.71429\times 10^{14}\; \rm s^{-1}$ .

The Planck's Constant can help find the energy of a photon given its frequency. Look up this constant to more than three significant figures:

$h \approx 6.62607\times 10^{-34}\; \rm J \cdot s^{-1}$ .

Calculate the energy of one such photon:

$\begin{aligned} E &= h \cdot f\\ &\approx 6.62607\times 10^{-34}\; \rm J \cdot s^{-1} \times 5.71023\times 10^{14}\; \rm s \\ &\approx 3.78370\times 10^{-19}\; \rm J \end{aligned}$ .

Calculate the number of these photons that $100\; \rm J$ of energy can produce under the assumption of $100\%$ conversion:

$\displaystyle \frac{100\; \rm J}{3.78370\times 10^{-19}\; \rm J} \approx 2.64\times 10^{20}$ .

(Rounded to three significant figures.)

7 0

3 years ago

The general formula for ____________ and ____________ are CnH2n+2 and CnH2n , respectively. Axial and equatorial hydrogen atoms

Margarita [4]

Answer:

Alkanes

Cycloalkanes

Ring flip

Lower

Angle

Equatorial

Axial

Explanation:

For alkanes, the general molecular formula is CnH2n+2 while for cycloalkanes, the general molecular formula is CnH2n.

The cycloalkanes could undergo a ring flip in which axial and equatorial hydrogen atoms are interconverted.

The lower energy conformation of alkanes is the anti conformation and not the gauche conformation due to steric strain.

When the bond angle in alkanes deviate from the ideal 109.5°, an angle strain has occurred.

For bulky groups, the equatorial position his preferred since it has more room than the axial position.

4 0

3 years ago

What is the change in enthalpy in joules when 5.44 x 10- mol of AgCl dissolves in water according to the following chemical equa

ra1l [238]

Answer:

$\Delta H=35.3J$

Explanation:

Hello,

In this case, since the dissolution of silver chloride involves a change in enthalpy of 65.5kJ per 1 mole when undergone, for 5.44x10⁻⁴ moles, the enthalpy change is:

$\Delta H=65.5\frac{kJ}{1mol}*5.44x10^{-4}mol\\ \\\Delta H=0.0353kJ*\frac{1000J}{1kJ}\\ \\\Delta H=35.3J$

Best regards.

4 0

3 years ago