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3 years ago

Can someone please help me with this asap, it’s due today please help me

Chemistry

1 answer:

hammer [34]3 years ago

7 0

Answer:

lol I hate chemical but let me give some advice

Explanation:

Please go on Khan Academy or look at your notes and I promise you can figure out! Seriously, I am trying to be helpful not like the annoying teacher that says "figure it out"

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In order to understand the prehistory of the Hawaiian island of Lana'i better, anthropologists Maria Sweeney, Melinda Allen, and

AleksandrR [38]

Answer:

500 years

Explanation:

The original carbon-14 was 100%, and after 100 years, it decays 1.202%. So after 100 years it goes to 98.798%, after more 100 years (200 years), it will be 97.596% (98.798 - 1.202), thus, after n 100 years "package", the percenatge will be:

100% - actual% = n*1.202

n = (100% - actual%)/1.202

n = (100% - 94%)/1.202

n = 4.992

So, the number of years is n*100 = 4.992*100 = 499.2 ≅ 500 years.

4 0

3 years ago

If 4.0 mol of NO and 4.0 mol of O2 are combined, how many moles

Masja [62]

4.0

i think it has something to do with molar ratios and finding the limiting reactant

4.0 mol NO * 2 mol NO2/2 mol NO = 4.0 moles of NO2

4.0 mol O2 * 2 mol NO2/1 mol O2 = 8.0 moles of NO2

so the limiting reactant (the reactant that runs out the quickest leaving an excess) is NO

once the limiting reactant is found, we can use that data for that substance to calculate the amount of product

4.0 mol NO * 2 mol NO2/2 mole NO = 4.0 moles of NO2

4 0

3 years ago

Air thermals are updrafts of warm air that rise from

Anastaziya [24]

Answer:

B. convection because warm air rises and cool air sinks.

Explanation:

The processes that enables birds to fly to higher altitudes without flapping their winds while riding air thermals is called convection.

Convection is one of the forms of heat transfer usually found in gases and liquids.

In convection density differences due to temperature changes causes the circulation.
Warm air is less dense and it is hotter.
It rises up from the surface where it is warmed
Cold air sinks to replace the warm air. Cold air form when the air loses its energy to the surrounding.
By virtue of this, birds are able to take advantage of it for their flight.

7 0

3 years ago

How many hydrogen atoms are in 5.40 mol of ammonium sulfide?

Lelu [443]

Answer Expert Verified
Assuming that the ammonium sulfide formula is (NH4)2S then you can see that there are 2 nitrogen, 8 hydrogen and 2 sulfur atoms for every ammonium sulfide.
Hope that helps

3 0

3 years ago

Which molecule has polar bonding and is nonpolar? A. H2O B. BF3 C. NH3 D. NCl3 E. CH2Cl2

Marina CMI [18]

Answer:

B. BF₃

Explanation:

All the molecules have polar bonds, but a molecule will be nonpolar if the molecule has the symmetry that makes the bond dipoles cancel.

To make the decision, we must

Draw the Lewis structure
Assign the VSEPR electron geometry
Determine the molecular shape.
Examine the symmetry of the molecule

===============

A. Water

Lewis structure = H-O-H (2 bonding pairs, 2 lone pairs)

Electron geometry = AX₂E₂ tetrahedral

Molecular geometry = bent

Symmetry (see Figure A): The two O-H bonds are polar, with their negative ends pointing towards the O. The horizontal components of the bond dipoles cancel, but the vertical components reinforce each other and give an upward pointing molecular dipole. This is a polar molecule with polar bonds.

===============

B. Boron trifluoride

Lewis structure = BF₃ (3 bonding pairs)

Electron geometry = AX₃, trigonal planar

Molecular geometry = trigonal planar

Symmetry (see Figure B): The three B-F bonds are polar, with their negative ends pointing towards the F. The horizontal components of the bond dipoles cancel, but the vertical components of the two downward -pointing dipoles reinforce each other and give a resultant that is equal and opposite to the upward dipole. Thus, the bond dipoles cancel. This is a nonpolar molecule with polar bonds.

===============

C. Ammonia

Lewis structure = :NH₃ (3 bonding pairs, 1 lone pairs)

Electron geometry = AX₃E, tetrahedral

Molecular geometry = trigonal pyramidal

Symmetry (see Figure C): The three N-H bonds are polar, with their negative ends pointing towards the N. The horizontal components of the bond dipoles cancel, but the vertical components reinforce each other and give an upward pointing molecular dipole. This is a polar molecule with polar bonds.

===============

D. Nitrogen trichloride

Lewis structure = :NCl₃ (3 bonding pairs, 1 lone pair)

Electron geometry = AX₃E, tetrahedral

Molecular geometry = trigonal pyramidal

Symmetry (see Figure D): The three N-Cl bonds are polar, with their negative ends pointing towards the Cl. The horizontal components of the bond dipoles cancel, but the vertical components reinforce each other and give a downward pointing molecular dipole. This is a polar molecule with polar bonds.

===============

E. Dichloromethane

Lewis structure = H₂CCl₂ (4 bonding pairs)

Electron geometry = AX₄, tetrahedral

Molecular geometry = tetrahedral

Symmetry (see Figure E): The two C-H bonds are nonpolar, but the two C-Cl bonds are polar with their negative ends pointing towards the Cl. The horizontal components of the bond dipoles cancel, but the vertical components reinforce each other and give a downward pointing molecular dipole. This is a polar molecule with polar bonds.

3 0

3 years ago