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Nana76 [90]
3 years ago
9

The atomic number of lead (Pb) is 82. Its mass number is 207. How many protons, neutrons, and electrons does this neutral atom o

f lead (Pb) contain?
Chemistry
1 answer:
AveGali [126]3 years ago
7 0
An element’s atomic number is equal to the number of protons in that element’s nucleus. The mass number is the total number of an atom’s protons and neutrons. Protons have a positive charge; electrons have a negative charge; and neutrons are electrically neutral.

Putting it all together, given that the atomic number of lead is 82, the number of protons a lead atom contains is 82. The number of neutrons would be the difference between 207 and 82, or 125 neutrons. Finally, since you have a neutral atom, there must be an equal number of electrons as the number of protons—that is, 82 electrons.

Thus, you’ve got 82 protons, 125 neutrons, and 82 electrons.
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The solubility of acetanilide is 12.8 g in 100 mL of ethanol at 0 ∘C, and 46.4 g in 100 mL of ethanol at 60 ∘C. What is the maxi
weqwewe [10]

Answer: 72.41% and 26.90% respectively.

Explanation:

At 60°C, you can dissolve 46.4g of acetanilide in 100mL of ethanol. If you lower the temperature, at 0°C, you can dissolve just 12.8g, which means (46.4g-12.8g)=33.6g of acetanilide must have precipitated from the solution.

We can calculate recovery as:

\%R=\frac{crystalized\ mass}{initial\ mass}*100 =\frac{33.6\ g}{46.4\ g}*100=72.41\%

So the answer to the first question is 72.41%.

For the second part just use the same formula, the mass of the precipitate is the final mass minus the initial mass, (171mg-125mg)=46mg.

\%R=\frac{crystalized\ mass}{initial\ mass}*100 =\frac{46\ mg}{171\ mg}*100=26.90\%

So the answer to the second question is 26.90%.

3 0
3 years ago
In a neutral atom, the number of protons is always equal to what other part of the atom?
Licemer1 [7]

Answer:

b. The number of electrons

Explanation:

A "neutral atom" has a <u>neutral charge</u>. This means that <em>its charge is equal to </em><em>zero. </em>In order for the charges to cancel out each other, the atom's <em>positive charge should be equal to the negative charge. </em>These being said, the number of electrons<em> (negatively-charged)</em> is then equal to the number of protons <em>(positively-charged). </em>Those atoms which are not neutral are called <em>"ions."</em> This means that they either have more or less electrons than the protons.

7 0
2 years ago
Using the thermodynamic information in the ALEKS Data tab, calculate the standard reaction free energy of the following chemical
julia-pushkina [17]

Answer:

43.0 kJ

Explanation:

The free energy (ΔG) measures the total energy that is presented in a thermodynamic system that is available to produce useful work, especially at thermal machines. In a reaction, the value of the variation of it indicates if the process is spontaneous or nonspontaneous because the free energy intends to decrease, so, if ΔG < 0, the reaction is spontaneous.

The standard value is measured at 25°C, 298 K, and the value of free energy varies with the temperature. It can be calculated by the standard-free energy of formation (G°f), and will be:

ΔG = ∑n*G°f products - ∑n*G°f reactants, where n is the coefficient of the substance in the balanced reaction.

By the balanced reaction given:

2NOCl(g) --> 2NO(g) + Cl2(g)

At ALEKS Data tab:

G°f, NOCl(g) = 66.1 kJ/mol

G°f, NO(g) = 87.6 kJ/mol

G°f, Cl2(g) = 0 kJ/mol

ΔG = 2*87.6 - 2*66.1

ΔG = 43.0 kJ

6 0
3 years ago
Please help!!!!its due tomorrow !!!
scZoUnD [109]

#6).
Every 1,000 mL makes 1 L
How many 1,000mL are there in  2,800 mL ?
That's division.
                         (2,800 mL) / (1,000 mL) = <em>2.8 L</em>

#7).
The 'perimeter' means the 'distance all the way around'.
You have to know that both sides of a rectangle are the same length,
and also the top and bottom are the same length.
So the perimeter of this rectangle is

   (2 yd) + (4.5 yd) + (2.yd) + (4.5 yd) = 13 yd .

Oops.  The problem wants to know the perimeter in feet.
So you have to know that each yard is the same as 3 feet.
In order to find the number of feet in 13 yards, you have to
take 3 feet 13 <em><u>times</u></em> .

       (3 feet) times (13)  =  <em>39 feet .</em>

#8).
For this one, you have to know that every 36 inches makes 1 yard.

How many 36 inches are there in 48 inches ?
That's division.
                         (48 inches) / (36inches)  =  <em>1 and 1/2 yards</em> .

#9).
For this problem, you have to know how to handle a mixed number,
and you also have to know that there are 16 ounces in 1 pound.

Add up the fruit:

             (3-1/2 pounds) + (4 pounds) + 2 pounds)  =  <em><u>9-1/2 pounds</u></em>

Now, remember that each pound is the same as 16 ounces.  So if you
want to find the number of ounces in  9-1/2 pounds, you have to take
16 ounces  9-1/2 times .

     (16 ounces) times (9-1/2) = <em>152 ounces</em>.
___________________________________

#10).
This one is just adding up some numbers.  But after you finish doing that, you have to know that  1,000 meters is called '1 kilometer' .

Add up the distances that Omar ran:

   (1,000 meters) + (1,625 meters) + (1,500 meters)  =  <em><u>4,125 meters</u></em>

The problem wants to know how many kilometers this is, so you have to figure out how many '1,000 meters' fit into 4,125 meters.

That's division.

   (4,125 meters) / (1,000 meters)  =  <em>4.125 kilometers</em>


4 0
3 years ago
A student has two unopened 33 CL cans containing carbonated water. Can A has been stored in the garage 32 degrees and can B has
IgorC [24]

Answer:

A. Can A will make a louder and stronger fizz than can B.  

Explanation:

The solubility of a gas in a liquid decreases as the temperature increases, so the warmer can will have more undissolved carbon dioxide.

The warmer can will be under greater pressure, so it will make a louder and stronger fizz.

7 0
3 years ago
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