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ser-zykov [4K]
3 years ago
12

Three elements are represented by the letters A, B, and C. the three elements have the same number of valence electrons. Element

C has electrons in three energy levels and element A is the lightest of the three. Elements B has a total of twenty electrons. Identify the elements.
Chemistry
1 answer:
AfilCa [17]3 years ago
3 0
Answer:
A- beryllium
B- calcium
C- magnesium

Explanation
NOTE: all element in group 2 have 2 balance electrons

First let’s start with B- number of electrons= number of protons which is equal to the atomic number. therefore, the answer is calcium as it’s atomic number is 20

C- magnesium will have three energy levels considering it has 12 electrons (2,8,2).

A- beryllium is the lightest one in group 2 as it has the atomic mass of 9.0122.
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elixir [45]
The correct answer that would best complete the given statement above would be option 2. <span>The relationship between molecular velocities and temperature is a direct relationship. In other words, their relationship is directly proportional. Hope that this is the answer that you are looking for. </span>
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The compound Fe2O3 contains how many atoms? <br> A) 2 <br> B) 3 <br> C) 5 <br> D) 7
marishachu [46]
The compound Fe2O3 contains C) 5 total atoms.

This is because there are 2 atoms of Fe (iron) and 3 atoms of O (oxygen) bonded together in this compound, as denoted by the subscripts, and 2+3 = 5.

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3 years ago
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If you have 30.O g of hydrogen gas burned in excess oxygen how many moles of water can you make
vladimir1956 [14]

Answer:

15 moles

Explanation:

Data given:

mass of hydrogen (H₂) = 30.0 g

amount of oxygen (O₂) = excess

moles of water = ?

Solution:

First we look to the reaction in which hydrogen react with oxygen and make (H₂O)

Reaction:

              2H₂  + O₂  -----------> 2H₂O

Now look at the reaction for mole ratio

             2H₂  + O₂  -----------> 2H₂O

             2 mole                       2 mole

So it is 2:2 mole ratio of hydrogen to water

As we Know

molar mass of H₂  = 2(1) = 2 g/mol

molar mass of H₂O = 2(1) + 16 = 18 g/mol

Now convert moles to gram

                  2H₂         +       O₂        ----------->    2H₂O

          2 mole (2 g/mol)                                 2 mole (18 g/mol)

                    4 g                                                     36 g

So,

we come to know that 4 g of hydrogen gives 36 g of water then how many grams of water will be produce by 30 grams of hydrogen.

Apply unity formula

                       4 g of H₂ ≅ 36 g of H₂O

                        30 g of H₂ ≅ X of H₂O

Do cross multiplication

                  X of H₂O =  30 g x 36 g / 4 g

                  X of H₂O =  270 g

Now convert grams of H₂O into moles

               No. of moles = mass in grams/molar mass

Put values in above formula

               No. of moles = 270 g / 18 (g/mol)

               No. of moles = 15 mol

so 30 gram of hydrogen produce 15 mol of water.

5 0
3 years ago
Number of molecules of baking soda
Softa [21]

Answer:

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8 0
2 years ago
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Type the correct answer in the box.
IgorLugansk [536]

Answer:

a= <em>In scientific notation</em>

6.96000×10⁵ Km

b =<em>In  expanded notation</em>

0.00019 mm

Explanation:

Given data:

Radius of sun = 696000 Km

size of bacterial cell = 1.9 ×10⁻⁴ mm

Radius of sun in scientific notation = ?

Size of bacterial cell in expanded notation = ?

Solution:

Scientific notation is the way to express the large value in short form.

The number in scientific notation have two parts.

. The digits (decimal point will place after first digit)

× 10 ( the power which put the decimal point where it should be)

for example the number 6324.4 in scientific notation will be written as = 6.3244 × 10³

Radius of sun:

696000 Km

<em>In scientific notation</em>

6.96000 × 10⁵ Km

The expanded notation is standard notation of writing the numerical values which is normal way. The numbers are written as they are, without the power of 10.

Size of bacterial cell:

1.9 ×10⁻⁴ mm

<em>In  expanded notation</em>

1.9/ 10000 = 0.00019 mm

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