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3 years ago

Why is melting an ice cube a reversible physical change?

Chemistry

1 answer:

Dmitriy789 [7]3 years ago

7 0

Answer:

Because you can freeze the water you melted back into a ice cube.

Explanation:

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Revision has a atoMic number of 37 and a mass number of 85. HIW many protons, neutrons and electrons does an ion of rubidium wit

EleoNora [17]

Answer: 37 protons, 48 neutrons, and 36 electrons.

Explanation: I assume "Revision" is Rubidium. It is atomic number 37, so it has 37 protons. It's atomic mass is 85, so it has an average of (85-37) = 48 neutrons. It has a charge of +1, so one electron of the original 37 has left.

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3 years ago

Marble is made from limestone under the influence of heat and pressure. The chemical formula for limestone or marble

evablogger [386]

Answer:

what is the gas that is produced.

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3 years ago

A solution of sulfuric acid is titrated with a solution of sodium hydroxide to the phenolphthalein end point. The sample of sulf

qaws [65]

Answer:

a. 2NAOH + H2SO4 —> NA2SO4 + 2H2O

b. The concentration of the acid is 0.0638M

Explanation:Please see attachment for explanation

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3 years ago

When metallic sodium is dissolved in liquid sodium chloride, electrons are released into the liquid. These dissolved electrons a

qaws [65]

Answer:

The edge of the length is $\mathbf{L = 8.54 \times 10^{-10} \ m}$

Explanation:

From the given information:

The associated energy for a particle in three - dimensional box can be expressed as:

$E_n = \dfrac{h^2}{8mL^2}(n_x^2+n_y^2+n_z^2)$

here;

h = planck's constant = $6.626 \times 10^{-34} \ Js$

$n_i$ = the quantum no in a specified direction

m = mass (of particle)

L = length of the box

At the ground state $n_x = n_y = n_z=1$

The energy at the ground state can be calculated by using the formula:

$E_1 =\dfrac{3h^2}{8mL^2}$

At first excited energy level, one of the quantum values will be 2 and the others will be 1.

Thus, the first excited energy will be: 2,1,1

∴

$E_2 =\dfrac{(2^2+1^2+1^2)h^2}{8mL^2}$

$E_2 =\dfrac{(4+1+1)h^2}{8mL^2}$

$E_2 =\dfrac{(6)h^2}{8mL^2}$

The transition energy needed to move from the ground to the excited state is:

$\Delta E= E_2 - E_1$

$\Delta E= \dfrac{6h^2}{8mL^2}- \dfrac{3h^2}{8mL^2}$

$\Delta E= \dfrac{3h^2}{8mL^2}}$ ----- (1)

Recall that:

the wavelength identified with the electronic transition is: 800 nm

800 nm = 8.0 × 10⁻⁷ m

However, the energy-related with the electronic transition is:

$\Delta E =\dfrac{hc}{\lambda}$

$\Delta E =\dfrac{6.626 \times 10^{-34} \times 2.99 \times 10^8}{8.0 \times 10^{-7} }$

$\Delta E =2.48 \times 10^{-19} \ J$

Replacing the value of $\Delta E$ in (1); then:

$2.48 \times 10^{-19}= \dfrac{3h^2}{8mL^2}}$

Making the edge length L the subject of the formula; we have:

$L = \sqrt{\dfrac{3h^2}{8m \times2.48 \times 10^{-19}} }$

$L = \sqrt{\dfrac{3\times (6.626 \times 10^{-34})^2}{8(9.1 \times 10^{-31} ) \times2.48 \times 10^{-19}} }$

$\mathbf{L = 8.54 \times 10^{-10} \ m}$

Thus, the edge of the length is $\mathbf{L = 8.54 \times 10^{-10} \ m}$

5 0

3 years ago

A 32 g sample of LiCl is dissolved in water to for 655 mL of solution. What is the molarity of the solution?

emmainna [20.7K]

Answer : The molarity of the solution is, 1.1 M LiCl

Explanation : Given,

Mass of $LiCl$ = 32 g

Volume of solution = 655 mL

Molar mass of $LiCl$ = 42.4 g/mole

Molarity : It is defined as the number of moles of solute present in one liter of volume of solution.

Formula used :

$\text{Molarity}=\frac{\text{Mass of }LiCl\times 1000}{\text{Molar mass of }LiCl\times \text{Volume of solution (in mL)}}$

Now put all the given values in this formula, we get:

$\text{Molarity}=\frac{32g\times 1000}{42.4g/mole\times 655mL}=1.1mole/L=1.1M$

Therefore, the molarity of the solution is, 1.1 M LiCl

3 0

3 years ago