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Vikentia [17]
3 years ago
12

Helium only has two valence electrons and is a stable atom. How is this possible when atoms

Chemistry
1 answer:
Andru [333]3 years ago
6 0

Answer:

Explanation:

Helium (He) is similar in that it, too, only has room for two electrons in its only valence shell. Hydrogen and helium have only one electron shell. The first shell has only one s orbital and no p orbital, so it holds only two electrons. Therefore, these elements are most stable when they have two electrons.

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During a combustion reaction, 9.00 grams of oxygen reacted with 3.00 grams of CH4.
Monica [59]

Answer:

0.74 grams of methane

Explanation:

The balanced equation of the combustion reaction of methane with oxygen is:

  • CH₄ + 2 O₂ → CO₂ + 2 H₂O

it is clear that 1 mol of CH₄ reacts with 2 mol of O₂.

firstly, we need to calculate the number of moles of both

for CH₄:

number of moles = mass / molar mass = (3.00 g) /  (16.00 g/mol) = 0.1875 mol.

for O₂:

number of moles = mass / molar mass = (9.00 g) /  (32.00 g/mol) = 0.2812 mol.

  • it is clear that O₂ is the limiting reactant and methane will leftover.

using cross multiplication

1 mol of  CH₄ needs → 2 mol of O₂

???  mol of  CH₄  needs → 0.2812 mol of O₂

∴ the number of mol of CH₄ needed = (0.2812 * 1) / 2 = 0.1406 mol

so 0.14 mol will react and the remaining CH₄

mol of CH₄ left over = 0.1875 -0.1406 = 0.0469 mol

now we convert moles into grams

mass of CH₄ left over = no. of mol of CH₄ left over *  molar mass

                                    = 0.0469 mol * 16 g/mol = 0.7504 g

So, the right choice is 0.74 grams of methane

3 0
3 years ago
Changes in the composition of the atmosphere have caused gradual changes in earth's _______ throughout history, causing changes
bearhunter [10]

climate

Changes in the composition of the atmosphere have caused gradual changes in earth's <u>climate</u> throughout history, causing changes in plant and animal life that contributed to mass extinctions.

The following are some of the reasons:

  • UV light
  • climate
  • pollutants
  • hydrofluorocarbons

heat

  • The surface of the Earth warms up as sunlight strikes it.
  • Surface-emitted infrared light is absorbed in the atmosphere and transformed into heat.
  • The temperature close to the surface rises as a result of this heat being trapped in the atmosphere.
<h3>UV light:</h3>
  • indirect impacts of climate change on UV radiation from the surface.
  • By changing the concentrations of ozone, UV-absorbing tropospheric gases, aerosols, and clouds in the atmosphere, climate change may have indirectly affected UV radiation levels in the past.
  • These influences are probably going to persist in the future.
<h3>climate:</h3>
  • People are at risk from food and water shortages, greater flooding, high heat, an increase in disease, and economic loss due to climate change.
  • Conflict and human migration are potential outcomes.
  • Climate change is the top hazard to world health in the twenty-first century, according to the World Health Organization (WHO).
<h3>pollutants:</h3>
  • these are also resulting in the increase of temperature of the Earth and is also damaging ozone layer.

To learn more about the changes in earth visit:

brainly.com/question/13434833?

#SPJ4

6 0
1 year ago
Scientific notation is
nataly862011 [7]

Scientific Notation Is Basically The Shorthand For Writing Numbers. Scientists Use It When They Want To Write Numbers That Are Very Big Or Very Small.  

4 0
3 years ago
Read 2 more answers
Please help ASAP please and thanks!! I'll also mark you!
skelet666 [1.2K]
Substitution Reactions are those reactions in which one nucleophile replaces another nucleophile present on a substrate. These reactions can take place via two different mechanism i.e SN¹ or SN². In SN¹ substitution reactions the leaving group leaves first forming a carbocation and nucleophile attacks carbocation in the second step. While in SN² reactions the addition of Nucleophile and leaving of leaving group take place simultaneously.
 
Example:
                        OH⁻  +  CH₃-Br     →     CH₃-OH  +  Br⁻

In above reaction,

                   OH⁻  = Incoming Nucleophile

                   CH₃-Br  =  Substrate

                   CH₃-OH  =  Product

                   Br⁻  =  Leaving group

Organic reactions are typically slower than ionic reactions because in organic compounds the covalent bonds are first broken, this breaking of bonds is a slower step, while, in ionic compounds no bond breakage is required as it consists of ions, so only bond formation takes place which is a quicker and fast step.
7 0
3 years ago
What is the molar concentration of hydronium ions in a sample of a soft drink that has a ph of 4?
hammer [34]

[H^{+}] value of soft drink is 0.0001mol/l when given pH is 4.

Given:

pH = 4

Needs to find: [H^{+}]

Formula to find: pH=−log_{10} [H^{+}]

We can put the values of pH in above formula as,

pH=−log_{10} [H^{+}]

4 =−log_{10} [H^{+}]

To calculate hydonium ion concentration, formula is as follows;

[H^{+}] = 10^{-pH}

[H^{+}] = 10^{-4} = 0.0001mol/l

[H^{+}] value of soft drink is 0.0001mol/l

Learn more about pH here:

brainly.com/question/2288405

#SPJ4

6 0
1 year ago
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