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julia-pushkina [17]
1 year ago
8

Calculate the atomic mass of X. The three X isotopes have atomic mass and relative abundances of 27.9769 amu (92.2297%), 28.9765

amu (4.6832%) and 29.9738 amu (3.0872%). What is this atom?
Co


Al


Ni


Si
Chemistry
1 answer:
Irina18 [472]1 year ago
7 0
<h3>Answer:  Si   (choice D)</h3>

This is the element Silicon.

=========================================================

Explanation:

First convert each percentage to its decimal form.

For example, 92.2297% converts to 0.922297 after moving the decimal point two spots to the left.

After doing that, multiply those decimal values with their respective atomic mass unit (amu) values.

  • 27.9769 * 0.922297 = 25.8030109393
  • 28.9765 * 0.046832 = 1.357027448
  • 29.9738 * 0.030872 = 0.9253511536

Then we add up the results

25.8030109393 + 1.357027448 + 0.9253511536 = 28.0853895409

That rounds to about 28.085

Then look at the periodic table to see the atomic mass of Cobalt (Co), Aluminum (Al), Nickel (Ni) and Silicon (Si). The mass values listed in the periodic table are weighted averages of all the isotopes. The units for the mass are still in amu.

  • Cobalt = 58.933
  • Aluminum = 26.982
  • Nickel = 58.693
  • Silicon = 28.085

We have a match with silicon, showing that <u>choice D</u> is the final answer.

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The term "periodic" helps identify __________ that occur in the table, like electronegativity or atomic radii.
Montano1993 [528]

Answer:

option C= patterns

Explanation:

The periodic table is helpful to identify the element readily. All the elements are arranged properly. The elements with same physical and chemical properties are placed in same group and period. Periodic table is also helpful to predict the properties of those elements which are not discovered yet. This table is also very helpful to balance the chemical equations. The horizontal rows are called periods while vertical column are called groups. There are seven periods and eighteen groups are in periodic table.

Trends in periodic table:

As we move left to right in a period the atomic radius is decreases with increase of atomic number. The ionization energy goes to increases from left to right in period because of greater hold of nuclear charge on valance electron, so that's way more energy is required to overcome this charge and to make the atom ionic.

From left to right in period electron affinity and electronegativity also increases.

As we move top to bottom in group ionization energy decreases with increase of atomic number  because of large atomic radius. The valance electron require less energy to move free. The electron affinity and electronegativity also decreases from top to bottom.

6 0
3 years ago
What is the concentration (in M) of a 225ml potassium sulfate solution that contains 4.15g of potassium?
mars1129 [50]

The concentration of solution in M or mol/L can be calculated using the following formula:

C=\frac{n}{V} .... (1)

Here, n is number of moles and V is volume of solution in L.

The molecular formula of potassium sulfate is K_{2}SO_{4} thus, there are 2 moles of potassium in 1 mol of potassium sulfate.

1 mol of potassium will be there in 0.5 mol of potassium sulfate.

Mass of potassium is 4.15 g, molar mass is 39.1 g/mol.

Number of moles can be calculated as follows:

n=\frac{m}{M}

Here, m is mass and M is molar mass

Putting the values,

n=\frac{(4.15 g}{(39.1 g/mol}=0.1061 mol

Thus, number of moles of  K_{2}SO_{4} will be 0.1061\times 0.5=0.053 mol.

The volume of solution is 225 mL, converting this into L,

1 mL=10^{-3}L

Thus,

225 mL=0.225 L

Putting the values in equation (1),

C=\frac{(0.053 mol}{0.225 L}=0.236 M

Therefore, concentration of potassium sulfate solution is 0.236 M.


4 0
3 years ago
Balanced equation for the neutralization of these 2. HCl , Ca(OH)2
Ghella [55]
Balanced equation:

<span>2 HCl + 1 Ca(OH)</span>₂<span> = 1 CaCl</span>₂<span> + 2 H</span>₂<span>O
</span>
hope this helps!


5 0
2 years ago
Read 2 more answers
Convert 7.1x10^25 molecules of water to moles
ruslelena [56]

Answer:

<h2>117.94 moles</h2>

Explanation:

To find the number of moles in a substance given it's number of entities we use the formula

n =  \frac{N}{L} \\

where n is the number of moles

N is the number of entities

L is the Avogadro's constant which is

6.02 × 10²³ entities

From the question we have

n =  \frac{7.1 \times  {10}^{25} }{6.02 \times  {10}^{23} }  \\  = 117.940199...

We have the final answer as

<h3>117.94 moles</h3>

Hope this helps you

8 0
2 years ago
How is the periodic table arranged
Mashcka [7]
The periodic table of elements arranges all of the known chemical elements in an informative array. Elements are arranged from left to right and top to bottom in order of increasing atomic number. Order generally coincides with increasing atomic mass. The rows are called periods.
8 0
2 years ago
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