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yulyashka [42]
3 years ago
15

Selah is making a mobile of an atom of beryllium to hang from the ceiling in her science class. She uses a clear plastic bag for

the nucleus and fills it with white foam balls for protons and black foam balls for neutrons. She suspends blue foam balls from strings around the nucleus to represent the electrons. Which diagram shows Selah's model?
Chemistry
1 answer:
mel-nik [20]3 years ago
7 0

Answer:

See explanation

Explanation:

The question is incomplete because the images of the models are absent. However, i will try to give you a general description of what the correct answer should be.

Beryllium is a member of group 2 in the periodic table. Beryllium has an atomic number of 4. This implies that it has four protons in its nucleus and four electrons in its shells. In a neutral atom, the number of electrons on the shells is equal to the number of protons in the nucleus.

The electronic configuration of Beryllium is 1s2 2s2. This implies that it should have two shells each containing only two electrons each.

Since we are using white foam balls for protons and black foam balls for neutrons, the clear plastic will contain four white foam balls and five  black foam balls since the mass number of beryllium is 9 and number of neutrons = mass number - number of protons.

Four blue foam balls hanging from strings will represent the electrons around the nucleus.

Any model that corresponds to the description above is the correct answer.

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8 0
3 years ago
7.7 cm<br> 9.8 cm<br> 0.00<br> 0.162 m
eimsori [14]

Answer:

Volume = 1222.5cm³

Explanation:

<em>If the question is about the volume of the rectangle:</em>

The volume of a rectangle is obtained by the multiplication of its 3 dimensions: Length, width, height.

In the problem, the length of the rectangle is 0.162m = 16.2cm

The width is 7.7cm

And the height is 9.8cm

The volume is:

Volume = 16.2cm*7.7cm*9.8cm

<h3>Volume = 1222.5cm³</h3>
5 0
3 years ago
Preparation of ammonia gas<br>​
Makovka662 [10]

Answer:

Ammonia is easily made in the laboratory by heating an ammonium salt, such as ammonium chloride NH4Cl with a strong alkali, such as sodium hydroxide or calcium hydroxide.

The gas may also be made by warming concentrated ammonium hydroxide.

Explanation:

2NH4Cl + Ca(OH)2 → CaCl2 + 2H2O + 2NH3(g)

7 0
2 years ago
An enzyme is a catalyst used by living things to promote and regulate chemical reactions. What is the most likely enzyme for the
dem82 [27]
I’m going to guess but B?
5 0
3 years ago
A 25.0 ml sample of 0.723 m hclo4 is titrated with a 0.27303 m koh solution. the h3o+ concentration after the addition of 66.2 m
tia_tia [17]
This doesn't need an ICE chart. Both will fully dissociate in water.

Assume HClO4 and KOH reacts with one another. All you need to do is determine how much HClO4 will remain after the reaction. Calculate pH.

Step 1:

write out balanced equation for the reaction

HClO4+KOH ⇔ KClO4 + H2O

the ratio of HClO4 to KOH is going to be 1:1. Each mole of KOH we add will fully react with 1 mole of HClO4

Step 2:

Determining the number of moles present in HClO4 and KOH

Use the molar concentration and the volume for each:
25 mL of 0.723 M HClO4

Covert volume from mL into L:
25 mL * 1L/1000mL = 0.025 L

Remember:

M = moles/L so we have 0.025 L of 0.723 moles/L HClO4

Multiply the volume in L by the molar concentration to get:

0.025L x 0.723mol/L = 0.0181 moles HClO4.

Add 66.2 mL KOH with conc.=0.273M
66.2mL*1L/1000mL = .0662 L
.0662L x 0.273mol/L = 0.0181 moles KOH

Step 3:

Determine how much HClO4 remains after reacting with the KOH.

Since both reactants fully dissociate and are used in a 1:1 ratio, we just subtract the number of moles of KOH from the number of moles of HClO4:

moles HClO4 = 0.0181; moles KOH = 0.0181, so 0.0181-0.0181 = 0

This means all of the HClO4 is used up in the reaction.

If all of the acid is fully reacted with the base, the pH will be neutral = 7.

Determine the H3O+ concentration:

pH = -log[H3O+]; [H3O+] = 10-pH = 10-7

The correct answer is 1.0x10-7.
3 0
3 years ago
Read 2 more answers
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