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Vilka [71]
2 years ago
15

Write the symbol for every chemical element that has atomic number greater than 8 and atomic mass less than 25.5 u.

Chemistry
1 answer:
timama [110]2 years ago
7 0

F  atomic number 9, mass 19

Ne  atomic number  10, mass 20

Na  atomic number 11, mass 23

Mg  atomic number 12, mass 24

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Two substances A and B, initially at different temperatures, are thermally isolated from their surroundings and allowed to come
Elden [556K]

Answer:

B

Explanation:

For solving this we need a heat balance

Q_{a} = Q_{b}\\m_{a}*C_{a}*\Delta T_{a} = m_{b}*C_{b}*\Delta T_{b}

By changing the corresponding relations, we have

m_{a}*C_{a}*\Delta T_{a} = \frac{1}{2}m_{a}*4C_{a}*\Delta T_{b} \\\\\\

By cancelling similar factor, we obtain

\Delta T_{a} = 2 \Delta T_{b}\\\frac{\Delta T_{a}}{\Delta T_{b}} = 2\\

Which means that the change of temperature in A is twice the change of B

3 0
3 years ago
The Quantum Mechanical Model is used to describe:
gayaneshka [121]

The quantum mechanical model is used to describe the energy and most likely location of an electron.

Answer: Option A

<u>Explanation: </u>

The quantum mechanical model leads to the introduction of quantum numbers representing the energy levels, sub-shells, orbitals as well as spin states of the electrons. So according to the quantum numbers we can perfectly define the position and energy of any electron in an element.

According to Pauli’s principle, any two electron cannot be having same set of quantum numbers. So, using the principle quantum number, azimuthal quantum number, magnetic and spin quantum number, we can define the energy and location of an electron in the atom.

5 0
3 years ago
You find a mysterious white powder in your kitchen. It could be cream of tartar (pH=5), sugar (pH=7), baking soda (pH=8), or dra
GREYUIT [131]

The pH indicators to be used are Phenolphthalein, Red cabbage, Bromthymol blue and Congo red.

<h3>What are pH indicators?</h3>

Indicators are substances which change color as the pH of a medium changes.

The common indicators and their pH range is as follows:

  • Phenolphthalein - pH range of 8.3 and 10.5
  • Red cabbage - pH 2 to 10
  • Bromthymol blue - 6.0 to 7.6
  • Congo red - 3.0 to 5.2

Therefore, the indicators to be used are Phenolphthalein, Red cabbage, Bromthymol blue and Congo red.

Learn more about pH indicators at: brainly.com/question/13779537

#SPJ1

8 0
2 years ago
Help please, wavelengths!:)
meriva
Answer b) a to c would be considered one wavelength.
3 0
3 years ago
Read 2 more answers
How many molecules of H2O and O2 is present in 8.5g of H2O?​
Igoryamba

Answer:

2.8 x 10²³ molecules H₂O

1.4 x 10²³ molecules O₂

Explanation:

First, you will need the balanced chemical equation for the formation of water:

2H₂ + O₂ -> 2H₂O

This will help in determining the mole ratios between water and oxygen, which we will need later.

Let's first calculate the number of H₂O (water) molecules. This will require stoichiometry. We are also given the mass, so we must convert mass into moles, then moles into molecules. mass -> moles -> molecules

8.5 g H₂O x (1 mol H₂O/18.01528 g H₂O) x (6.02 x 10²³ molecules H₂O/1 mol H₂O) = 2.8404 x 10²³ molecules H₂O

Rounded to 2 significant digits: 2.8 x 10²³ molecules H₂O

Now, to find the molecules of water, we can begin with the same stoichiometric equation, but before we convert to molecules, we will have to convert moles of water to moles of oxygen. This is where we will use the mole ratio of water to oxygen we got from the balanced chemical equation earlier. 2H₂O:1O₂

8.5 g H₂O x (1 mol H₂O/18.01528 g H₂O) x (1 mol O₂/2 mol H₂O) x (6.02 x 10²³ molecules O₂/1 mol O₂) = 1.4202 x 10²³ molecules O₂

Rounded to 2 significant digits: 1.4 x 10²³ molecules O₂

3 0
3 years ago
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