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4 years ago

I NEED HELP PLEASE, THANKS SO MUCH! :)

Chemistry

1 answer:

Anon25 [30]4 years ago

7 0

Answer:

Here's what I get

Explanation:

The molecules of a substance attract each other.

They are also in constant motion.

Their kinetic energy increases with the temperature.

1. Solids

If the temperature is low enough, the molecules will have little kinetic energy.

They will not be able to escape the attractions of their neighbours, so they will be fixed in place in a crystalline array.

All they can do is vibrate about their position in the array.

The substance will be a solid.

2. Liquids

If the temperature is higher, the molecules will have enough kinetic energy to slide past each other, but not enough to escape the attractions of nearby molecules.

The substance will be a liquid.

3. Gases

If the temperature is high enough, the molecules will have enough kinetic energy to escape from the surface and fly off into space.

The molecules will on average so far apart that they won't feel the attractions of others.

When they do collide, they will have energy to bounce off each other rather than stick together.

The substance will be a gas.

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Determine the packing efficiency of a simple cubic unit cell that contains one atom with a metallic radius of 175 pm.

PilotLPTM [1.2K]

Answer:

the packing efficiency is 52.36%

Explanation:

Given the data in the question;

simple cubic unit cell that contains one atom with a metallic radius of 175 pm;

we know that;

Edge length of Simple cubic (a) is related to radius of atom (r) as follows;

a = 2r

since radius r = 175 pm

we substitute

a = 2 × 175 pm

a = 350 pm

Now we get the volume unit;

Volume of unit cell = a³ = ( 350 pm ) = 42875000 pm³

Next we get Volume of sphere;

Volume of Sphere = $\frac{4}{3}$ πr³

Volume occupied by 1 atom = $\frac{4}{3}$ × π × ( 175 pm )³

= $\frac{4}{3}$ × π × 5359375 pm³

= 22449297.5 pm³

Now, the packing efficiency = ( Volume occupied by 1 atom / Volume of unit cell ) × 100

we substitute;

packing efficiency = ( 22449297.5 pm³ / 42875000 pm³ ) × 100

= 0.523598 × 100

= 52.36%

Therefore, the packing efficiency is 52.36%

8 0

3 years ago

What is valency pls i need it now

Tanzania [10]

Valency is the number of electrons present in the outermost shell.

5 0

3 years ago

Read 2 more answers

What is the kinetic energy, in joules, of a molecule of carbon tetrachloride moving at a speed of 255 m s–1 (use the appropriate

hram777 [196]

Answer:

The kinetic energy of a molecule of carbon tetrachloride is 8.29 zJ.

Explanation:

The kinetic energy of a molecule of carbon tetrachloride is given by:

$K = \frac{1}{2}mv^{2}$

Where:

m: is the mass

v: is the speed = 255 m/s

To find the mass we need to find the molar mass for CCl₄, and use the Avogadro's number, knowing that in 1 mol of carbon tetrachloride we have 6.022x10²³ molecules:

A (C) = 12.011 g/mol

A (Cl) = 35.45 g/mol

The molar mass (M) of CCl₄ is:

$M = A (C) + 4*A (Cl) = 12.011 g/mol + 4*35.45 g/mol = 153.81 g/mol$

Now, the mass of 1 molecule of CCl₄ is:

$m = 153.81 \frac{g}{mol}*\frac{1 mol}{6.022 \cdot 10^{23} molecules} = 2.55 \cdot 10^{-22} g = 2.55 \cdot 10^{-25} kg$

Finally, the kinetic energy of a molecule of carbon tetrachloride is:

$K = \frac{1}{2}mv^{2} = \frac{1}{2}2.55 \cdot 10^{-25} kg*(255 m/s)^{2} = 8.29 zJ$

Therefore, the kinetic energy of a molecule of carbon tetrachloride is 8.29 zeptoJoule.

I hope it helps you!

6 0

3 years ago

Give at least one example of how mass and weight are the same. (science)

Paha777 [63]

Answer:

The mass of an object is the same no matter where it is, but the weight of an object changes with the location of that object. For example, the weight of an object on the Moon is 1/6th that of the same object on Earth, while the mass of that object is exactly the same in both places.

Explanation:

Sited: https://howthingsfly.si.edu/ask-an-explainer/what’s-difference-between-mass-and-weight

6 0

4 years ago

Is chalk impermeable or permeable?

Gemiola [76]

Answer:

Permeable.

Explanation:

Most sediments of a chalky quality are permeable.

3 0

3 years ago

Read 2 more answers