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Harrizon [31]
3 years ago
12

When was the death of all dinosuars?

Chemistry
1 answer:
liberstina [14]3 years ago
4 0
The Cretaceous-Tertiary extinction event , the name given to the die off dinosaurs, they all died off about 65.5 million years ago . They died by climate and geological changes .
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True or false: SOLIDS have a definite shape, a definite volume, and cannot flow.
pychu [463]

This statement is true.

6 0
3 years ago
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1. Calculate the energy of a photon with a frequency of 3x1015 Hz.<br> ?????
Afina-wow [57]

Answer:

1.99 x 10⁻¹⁸J

Explanation:

Given parameters:

Frequency of the wave  = 3 x 10¹⁵Hz

Unknown:

Energy of the photon  = ?

Solution:

To solve this problem, we use the expression below;

     E  = hf

Where E is the energy, h is the Planck's constant and f is the frequency

Now insert the parameters and solve for E;

     E  = 6.63 x 10⁻³⁴ x 3 x 10¹⁵ = 19.9 x 10⁻¹⁹J or 1.99 x 10⁻¹⁸J

6 0
3 years ago
Pre-Lab Study Questions / 9
jok3333 [9.3K]

Answer:

See detailed answer with explanation below.

Explanation:

Valence electrons are electrons found on the outermost shell of an atom. They are the electrons in an atom that participate in chemical combination. Recall that the outermost shell of an atom is also referred to as its valence shell. Let us consider an example; if we look at the atom, sodium-11, its electronic configuration is 2,8,1. The last one electron is the valence electron of sodium which is found in its outermost or valence shell.

Positive ions are formed when electrons are lost from the valence shell of an atom. For instance, if the outermost electron in sodium is lost, we now form the sodium ion Na^+ which is a positive ion. Positive ions possess less number of electrons compared to their corresponding atoms.

Negative ions are formed when one or more electrons is added to the valence shell of an atom. A negative ion possesses more electrons than its corresponding atom. For example, chlorine(Cl) contains 17 electrons but the chloride ion (Cl^-) contains 18 electrons.

In molecular compounds, a bond is formed when two electrons are shared between the bonding atoms. Each bonding atom may contribute one of the shared electrons (ordinary covalent bond) or one of the bonding atoms may provide the both shared electrons (coordinate covalent bond). The shared pair may be located at an equidistant position to the nucleus of both atoms. Similarly, the electron may be drawn closer to the nucleus of one atom than the other (polar covalent bond) depending on the electro negativity of the two bonding atoms.

The electrons are shared in order to complete the octet of each atom by so doing, the both bonding atoms now obey the octet rule. For example, two chlorine atoms may come together to form a covalent bond in which each chlorine atom has an octet of electrons on its outermost shell.

4 0
3 years ago
Which type of changes are melting, freezing, and boiling?​
tatiyna

Answer:

Adding heat.

Decreasing and increasing temperatures.

Explanation:

4 0
2 years ago
Read 2 more answers
Calculate the mass of CO2 that can be produced if the reaction of 54.0 g of propane and sufficient oxygen has a 64.0% yield.
Oduvanchick [21]

Answer:

103.9 g

Explanation:

  • C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

First <u>we convert 54.0 g of propane (C₃H₈) into moles</u>, using its <em>molar mass</em>:

  • 54.0 g ÷ 44 g/mol = 1.23 mol C₃H₈

Then we <u>convert 1.23 moles of C₃H₈ into moles of CO₂</u>, using the <em>stoichiometric coefficients</em>:

  • 1.23 mol C₃H₈ * \frac{3molCO_2}{1molC_3H_8} = 3.69 mol CO₂

We <u>convert 3.69 moles of CO₂ into grams</u>, using its <em>molar mass</em>:

  • 3.69 mol CO₂ * 44 g/mol = 162.36 g

And <u>apply the given yield</u>:

  • 162.36 g * 64.0/100 = 103.9 g
7 0
2 years ago
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