1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
dalvyx [7]
3 years ago
15

Which of these pairs of elements have the same number of valence electrons?

Chemistry
1 answer:
ElenaW [278]3 years ago
6 0
The correct answer is the second option; sodium (Na) and potassium (K.)
Both sodium and potassium have the same number of valence electrons. 
You might be interested in
Suppose a group of volunteers is planning to build a park near a local lake. The lake is known to contain low levels of arsenic
ale4655 [162]

A) 10.75 is the concentration of arsenic in the sample in parts per billion .

B) 7,633.66 kg the total mass of arsenic in the lake that the company have to remove.

C)It will take 1.37 years to remove all of the arsenic from the lake.

Explanation:

A) Mass of arsenic in lake water sample = 164.5 ng

The ppb is the amount of solute (in micrograms) present in kilogram of a solvent. It is also known as parts-per million.

To calculate the ppm of oxygen in sea water, we use the equation:

\text{ppb}=\frac{\text{Mass of solute}}{\text{Mass of solution}}\times 10^9

Both the masses are in grams.

We are given:

Mass of arsenic = 164.5 ng = 164.5\times 10^{-9} g

1 ng=10^{-9} g

Volume of the sample = V = 15.3 cm^3

Density of the lake water sample ,d= 1.00 g/cm^3

Mass of sample =  M = d\times V=1.0 g/cm^3\times 15.3 cm^3=15.3 g

ppb=\frac{164.5\times 10^{-9} g}{15.3 g}\times 10^9=10.75

10.75 is the concentration of arsenic in the sample in parts per billion.

B)

Mass of arsenic in 1 cm^3  of lake water = \frac{164.5\times 10^{-9} g}{15.3}=1.075\times 10^{-8} g

Mass of arsenic in 0.710 km^3 lake water be m.

1 km^3=10^{15} cm^3

Mass of arsenic in 0.710\times 10^{15} cm^3 lake water :

m=0.710\times 10^{15}\times 1.075\times 10^{-8} g=7,633,660.130 g

1 g = 0.001 kg

7,633,660.130 g = 7,633,660.130 × 0.001 kg=7,633.660130 kg ≈ 7,633.66 kg

7,633.66 kg the total mass of arsenic in the lake that the company have to remove.

C)

Company claims that it takes 2.74 days to remove 41.90 kilogram of arsenic from lake water.

Days required to remove 1 kilogram of arsenic from the lake water :

\frac{2.74}{41.90} days

Then days required to remove 7,633.66 kg of arsenic from the lake water :

=7,633.66\times \frac{2.74}{41.90} days=499.19 days

1 year = 365 days

499.19 days = \frac{499.19}{365} years = 1.367 years\approx 1.37 years

C)

Company claims that it takes 2.74 days to remove 41.90 kilogram of arsenic from lake water.

Days required to remove 1 kilogram of arsenic from the lake water :

\frac{2.74}{41.90} days

Then days required to remove 7,633.66 kg of arsenic from the lake water :

=7,633.66\times \frac{2.74}{41.90} days=499.19 days

1 year = 365 days

499.19 days = \frac{499.19}{365} years = 1.367 years\approx 1.37 years

It will take 1.37 years to remove all of the arsenic from the lake.

6 0
3 years ago
How do electrons differ from protons and neutrons? A. They do not move. B. They are larger. C. They are not in a fixed position.
nikdorinn [45]
Hi!

Electrons are particles which basically 'orbit' around the nucleus. Protons and neutrons are condensed, in a fixed position inside the nucleus. 

With this in mind, the answer will be C.

Hopefully, this helps! =)
4 0
3 years ago
Read 2 more answers
Consider the chemical equation below. Upper M g (upper O upper H) subscript 2 plus 2 upper H upper N upper O subscript 3 right a
masha68 [24]

Answer:

Upper H superscript plus, plus upper O upper H superscript minus right arrow upper H subscript 2 upper O.

Explanation:

i just took the test , i hope this helps:)

8 0
3 years ago
Read 2 more answers
Which measure of a gas does the expression nRT represent? (1 point)
DaniilM [7]
The Ideal Gas Equation
The term pVnRT is also called the compression factor and is a measure of the ideality of the gas. An ideal gas will always equal 1 when plugged into this equation……
7 0
2 years ago
1.24 moles of magnesium arsenate are dissolved in 1.74 kg of solution. Calculate the molality of the solution.
aleksklad [387]

Answer:

Molality of the solution = 0.7294 M

Explanation:

Given:

Number of magnesium arsenate = 1.24 moles

Mass of solution = 1.74 kg

Find:

Molality of the solution

Computation:

Molality of the solution = Mole of solute / Mass of solution = 1.74 kg

Molality of the solution = 1.24 / 1.7

Molality of the solution = 0.7294 M

6 0
3 years ago
Other questions:
  • Number the elements sodium, magnesium, phosphorus, and chlorine in the predicted order ionization energies from the highest to t
    11·2 answers
  • Which of these groups of elements show the least electronegativity?
    9·2 answers
  • Sketch the structure of the nitrogen containing product that is formed when ethalymine reacts with water.
    6·1 answer
  • Which of the following takes place during a redox reaction? A. Electrons are gained only. B. Electrons are lost only. C. Electro
    8·2 answers
  • Which of the following statements best describes why electrons
    5·1 answer
  • Please please help :/
    9·2 answers
  • why is sodium chloride solution a good conductor of electricity but does not have any effect on litmus paper?​
    6·1 answer
  • Which statement describes a characteristic of a question that can be answered through scientific inquiry
    8·1 answer
  • Which type of molecule is made from nucleotides?
    9·1 answer
  • 2 True or False. The speed of light is sped up by dense media.​
    13·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!