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3 years ago

Help pls, it's a test about fossils?

Chemistry

1 answer:

Anna71 [15]3 years ago

6 0

Answer:

C. At some point, the land was covered in water.

Explanation:

In the diagram it shows the different fossil layers. In the bottom layers there are shells, but as you go up the fossils start changing. This shows that there used to be water there, but now it is land.

You might be interested in

Explain the effects that different frequencies of electromagnetic radiation have when absorbed by matter.

Neko [114]

In order to answer this question we might first want to think about what is electromagnetic radiation. In essence it’s light, just some of the wavelengths are too long or too short for us to see.

We can think about it as two oscillating sinusoidal (goes up and down) waves, one is electric, the other is magnetic.

Because we’re dealing in waves, that means we can calculate their frequency, wavelength, amplitude (brightness) and period.

To calculate it we can use E=hc/lambda
Where E = jewels of energy
h = Planck’s constant
c = speed of light
Lambda = wavelength

It doesn’t really matter for this question what those things mean, just note that it takes more energy to have a shorter wavelength, or less energy to have a longer wavelength.

So now we can answer the question. Light of a longer wavelength has less energy than that of a shorter wavelength. So, when long wavelengths are absorbed by matter (atoms) they will give those atoms less energy. So, either it will pass through the object entirely or it will make the atoms vibrate a little bit more than they already are and we call that thermal energy, or heat.

If high energy wavelengths are passing through matter then they will be giving those atoms a lot of energy, sometimes even ionizing the atoms.
Which, if you’re a living thing can be very bad for your cells.

I hope that helps.

8 0

4 years ago

How may moles are in 145.54 g of SIO2

KonstantinChe [14]

Answer:

The number of mole is 2.422 moles

Explanation:

To calculate the number of mole, we have to use the formula n = m /Mm

n - moles

m - mass

Mm - molar mass

Let's calculate the molar mass of the compound SiO2

Si - 28.0855

O - 15.999

Note: there are two atoms of oxygen in the compound

Mm of SiO2= 28.0855+ 2* 15.999

= 60.0835g/mol

Now, we calculate the number of moles

n = 145.54g/ 60.0835g/mol

= 2.422mol

8 0

3 years ago

What is the mole ratio of O2 to H2O in this reaction? 4NH3 + 5O2 → 4NO + 6H2O ?

Fed [463]

The answer is c O2:H2O
502:6H2O
SO THAT IS 5:6

4 0

3 years ago

A 25.00 ml sample of an aqueous solution of ba(oh)2 requires 18.45 ml of 0.01500 m hcl (aq) for its neutralization. what is the

klio [65]

5.54 x 10⁻³ M

<h3>Further explanation</h3>

Given:

Neutralization reaction between:

25.00 ml of Ba(OH)₂
18.45 ml of 0.015 M HCl

Question:

What is the molarity of the Ba(OH)₂ solution?

The Process:

Let us say the molarity of the Ba (OH)₂ solution as x M.

Step-1: prepare moles for each reagent

$\boxed{ \ M = \frac{n}{V} \ }$ $\rightarrow \boxed{ \ n = MV \ }$

$\boxed{ \ Ba(OH)_2 \rightarrow n = (x \ \frac{mol}{L})(25 \ ml) = 25x \ mmol \ }$

$\boxed{ \ HCl \rightarrow n = (0.015 \ \frac{mol}{L})(18.45 \ ml) = 0.277 \ mmol \ }$

Step-2: neutralization

We use the ICE table to see how neutralization occurs between acid and base.

Balanced reaction:

$\boxed{ \ Ba(OH)_2_{(aq)} + 2HCl_{(aq)} \rightarrow BaCl_2_{(aq)} + 2H_2O_{(l)} \ }$

Initial: 25x 0.277 - -

Change: - ¹/₂ · (0.277) -0.277 +¹/₂ · (0.277) +0.277

Equlibrium: - - +¹/₂ · (0.277) +0.277

Neutralization causes no excess of hydrogen or hydroxide ions in solution. In the end, the number of acid and base reactions is balanced. In other words, the two reagents have run out with nothing left.
HCl acts as a limiting reagent.

Step-3: calculate the molarity of the Ba(OH)₂ solution.

We consider Ba (OH) from the initial, change, and equilibrium stages.

$\boxed{ \ 25x - \frac{1}{2}(0.277) = 0 \ }$

$\boxed{ \ 25x = \frac{1}{2}(0.277) \ }$

$\boxed{ \ 50x = 0.277 \ }$

$\boxed{ \ x = \frac{0.277}{50} \ }$

$\boxed{ \ x = 5.54 \times 10^{-3} \ }$

Thus, the molarity of the Ba(OH)₂ solution is 5.54 x 10⁻³ M.

_ _ _ _ _ _ _ _ _ _

Alternative Steps

Valence of base = the number of OH⁻ ions
Valence of acid = the number of H⁺ ions

Neutralization: $\boxed{ \ V_b \cdot M_b \cdot valence \ of \ base = V_a \cdot M_a \cdot valence\ of \ acid \ }$

$\boxed{ \ (25.00 \ ml) \cdot x \cdot 2 = (18.45 \ ml) \cdot (0.015 \ M) \cdot 1 \ }$

$\boxed{ \ x = \frac{(18.45 \ ml) \cdot (0.015 \ M)}{(25.00 \ ml) \cdot 2} \ }$

Thus the same results were obtained. The molarity of Ba (OH) ₂ solution is 5.54 x 10⁻³ M.

<h3>Learn more</h3>

What is the concentration of a solution formed by diluting 25.0 ml of a 3.2 M NaCl solution to 135.0 ml? brainly.com/question/12452615
How much of these solutions he needs to drain and replace with 70% acid solution to obtain 100g of 60% acid solution? brainly.com/question/7596086
How many liters of the 50% solution and how many liters of the 90% solution will be used? brainly.com/question/13034221

6 0

4 years ago

You have been injured in the laboratory (cut,burn,etc) first you should

Sunny_sXe [5.5K]

Let the teacher know

8 0

3 years ago

Read 2 more answers