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Kisachek [45]
3 years ago
9

How many moles in 4.65 g of Helium?

Chemistry
1 answer:
Maru [420]3 years ago
7 0

Answer:

4.65 g x 1 mol/4.0026 g/mol = 1.162 mol helium

Explanation:

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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
The table describes how some substances were formed.
lisabon 2012 [21]

Explanation:

Which is a pure substance?

1. soda

2. gasoline

3. salt water

4. carbon dioxide

carbon dioxide

Bromine, a liquid at room temperature, has a boiling point of 58°C and a melting point of -7.2°C. Bromine can be classified as a

1. compound.

2. impure substance.

3. mixture.

4. pure substance.

pure substance.

6 0
4 years ago
Read 2 more answers
If you complete and balance the following oxidation-reduction reaction in basic solution NO2−(aq) + Al(s) → NH3(aq) + Al(OH)4−(a
andreev551 [17]

Answer:

NO2- + 5H2O + 2Al + OH- → NH3 + 2Al(OH)4-

There is 1 hydroxide ion, on the reactant side

Explanation:

NO2−(aq) + Al(s) → NH3(aq) + Al(OH)4−(aq)

Step 1: The half reactions

NO2- (aq) → NH3(g)

Al(s) → Al(OH)4-

<u>Step 2: </u>Balancing electrons

NO2- → NH3

On the left side N has an oxidation number of +3 and on the right side -3.

NO2- +6e-→ NH3

Al(s) → Al(OH)4-

On the left side, Al has an oxidation number of 0 and on the right side +3.

Al(s) → Al(OH)4- +3e-

To have the same amount of electrons transfered, we have to multiply the second reaction by 2

NO2- +6e-→ NH3

2(Al(s) → Al(OH)4- +6e-)

<u>Step 3:</u> Balance with OH/H2O

NO2- +6e +5H2O → NH3 +7OH-

2Al +8OH- → 2Al(OH)4- + 6e-

<u>Step 4:</u> The netto reaction

NO2- + 5H2O + 2Al + 8OH-  → NH3 +7OH- + 2Al(OH)4-

NO2- + 5H2O + 2Al + OH- → NH3 + 2Al(OH)4-

There is 1 hydroxide ion, on the reactant side

6 0
4 years ago
When a scientific theory has been tested and proved by the scientific community, it becomes a law.
suter [353]

Answer:

False

Explanation:

Because laws and theories are developed for different purposes, laws never become theories, and theories do not become laws.

4 0
2 years ago
Which pair of elements would most likely combine to form a salt?
jekas [21]

Answer:

Na Cl ?

Explanation:

None of them but Sodium and Chlorine does make salt i think thats what you meant.

8 0
3 years ago
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