Please help me do three

What is density? what does it tell you about substance?

Alekssandra [29.7K]

Hello!

Explanation:

↓↓↓↓↓↓↓

Density is the amount of mass in a given volume. It's a derived unit of measure. It is equal to mass divided by volume. It's measured in units such as grams per cubic centimeter and grams per milliliter. Density is the ratio of mass to volume. Density is a physical property of an object. It is degree of compactness of a substances. Relative density is used to separate solids, liquids, and gases. The gas in the container rises to the top because it has the least density. The liquids separate into individual layers based on their relative densities. The least dense liquid is on top. The most dense liquid is on bottom. The solids sink to the bottom of the container because they have the greatest density.

Hope this helps!

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-Charlie

4 0

2 years ago

What net ionic equation describes the reaction when these solutions are mixed?

almond37 [142]

I think the correct answer from the choices listed above is option D. The net ionic equation that will describe the reaction of the reactants when mixed is expressed as:

<span>2PO43–(aq) + 3Ca2+(aq) → Ca3(PO4)2(s)
</span>
Hope this answers the question. Have a nice day.

7 0

3 years ago

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What does Newton’s first law of motion state?

Troyanec [42]

Answer:

Newton's first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. This is normally taken as the definition of inertia. ... If that velocity is zero, then the object remains at rest.

Explanation:

6 0

2 years ago

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Calculate the frequency of the n=2 line in the lyman series of hydrogen

Alona [7]

Answer:

Approximately $2.47\times 10^{15}\; \rm Hz$ .

Explanation:

The Lyman Series of a hydrogen atom are due to electron transitions from energy levels $n \ge 2$ to the ground state where $n = 1$ . In this case, the electron responsible for the line started at $n = 2$ and transitioned to

A hydrogen atom contains only one electron. As a result, Bohr Model provides a good estimate of that electron's energy at different levels.

In Bohr's Model, the equation for an electron at energy level $n$ (

$\displaystyle - \frac{k\, Z^2}{n^2}$ (note the negative sign in front of the fraction,)

where

$k = 2.179 \times 10^{-18}\; \rm J$ is a constant.

$Z$ is the atomic number of that atom. $Z = 1$ for hydrogen.
$n$ is the energy level of that electron.

The electron that produced the $n = 2$ line was initially at the

$\begin{aligned} &E_{n = 2} \cr &= -\frac{k\, Z^2}{n^2} \cr &= -\frac{2.179 \times 10^{-18} \times 1}{2^2} \cr & \approx -5.4475\times 10^{-19}\; \rm J\end{aligned}$ .

The electron would then transit to energy level $n = 1$ . Its energy would become:

$\begin{aligned} &E_{n = 1} \cr &= -\frac{k\, Z^2}{n^2} \cr &= -\frac{2.179 \times 10^{-18} \times 1}{1^2} \cr & \approx -2.179 \times 10^{-18} \; \rm J\end{aligned}$ .

The energy change would be equal to

$\begin{aligned}&\text{Initial Energy} - \text{Final Energy} \cr &= E_{n = 2} - E_{n = 1} \cr &= -5.4475 \times 10^{-19} - \left(-2.179 \times 10^{-18}\right) \cr & \approx 1.63425\times 10^{-18}\; \rm J \end{aligned}$ .

That would be the energy of a photon in that $n = 2$ spectrum line. Planck constant $h$ relates the frequency of a photon to its energy:

$E = h \cdot f$ , where

$E$ is the energy of the photon.
$h \approx 6.62607015\times 10^{-34}\; \rm J \cdot s$ is the Planck constant.
$f$ is the frequency of that photon.

In this case, $E \approx 1.63425 \times 10^{-18}\; \rm J$ . Hence,

$\begin{aligned} f &= \frac{E}{h} \cr &\approx \frac{1.63425\times 10^{-18}}{6.62607015\times 10^{-34}} \cr & \approx 2.47 \times 10^{15}\; \rm s^{-1}\end{aligned}$ .

Note that $1 \; \rm Hz = 1 \; \rm s^{-1}$ .

6 0

3 years ago

What are the building blocks of starch molecules

murzikaleks [220]

Answer:

Glucose is the building block for starch

Explanation:

(amylose and amylopectin)

8 0

2 years ago