CHEMISTRY HIGH SCHOOL

Which is a physical change?A)
burning wood
Eliminate
B)
rusting metal
C)
cooking an egg
D)
freezing water

Answers

Answer 1
Answer: Freezing water is an example of a physical change
Answer 2
Answer:

freezing water,answer choice d

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Molecules in all organisms are composed in part of radioactive carbon-14. Which statement best explains the presence of carbon-14 in organisms?a. The radioactive isotope reacts in the same way as stable isotopes in the nuclear reactions in the body.
b. The radioactive isotope reacts in the same way as stable isotopes in the chemical reactions in the body.
c. The radioactive isotope reacts faster than stable isotopes in the nuclear reactions in the body.
d. The radioactive isotope reacts faster than stable isotopes in the chemical reactions in the body.

Answers

I think the correct answer from the choices listed above would be option B. The statement that best describes the presence of carbon-14 in organisms would be that radioactive isotope reacts in the same way as stable isotopes in the chemical reactions in the body. This seems to be the most suitable answer since the other choices suggest that there are nuclear reactions in our system which is very far from the truth.

The statement that best explains the presence of carbon-14 in organisms is that the radioactive isotope reacts in the same way as stable isotopes in the chemicalreactions in the body. That is option B.

What is radioactive carbon-14?

Radioactive carbon-14 is a type of radioactive element that is present in the air which is assimilated in small quantities into the body during metabolism( chemical reaction of the body).

The radioactive carbon-14. can be used in a process called carbon dating because it reacts the same way as stable isotopes in their chemical reactions in the body.

Learn more about radioisotopes here:

brainly.com/question/2320811

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If 4.00 g of NaCl react with 10.00 g of AgNO3, what is the excess reactant?

Answers

Answer : The excess reagent is, NaCl

Explanation :

First we have to calculate the moles of NaCl and AgNO_3.

\text{Moles of }NaCl=\frac{\text{Mass of }NaCl}{\text{Molar mass of }NaCl}=(4g)/(58.4g/mole)=0.068moles

\text{Moles of }AgNO_3=\frac{\text{Mass of }AgNO_3}{\text{Molar mass of }AgNO_3}=(10g)/(169.9g/mole)=0.058moles

Now we have to calculate the limiting and excess reagent.

The balanced chemical reaction is,

NaCl+AgNO_3\rightarrow AgCl+NaNO_3

From the balanced reaction we conclude that

As, 1 mole of NaCl react with 1 mole of AgNO_3

So, 0.068 moles of NaCl react with 0.068 moles of AgNO_3

From this we conclude that, the moles of AgNO_3 are less than the NaCl. So, AgNO_3 is a limiting reagent because it limits the formation of products and NaCl is an excess reagent.

Hence, the excess reagent is, NaCl
The reaction formula of this is NaCl + AgNO3 = NaNO3 + AgCl. The mole number of NaCl is 4/58.5=0.068 mol. The mole number of AgNO3 is 10/170=0.059 mol. So the NaCl is excess.

Atomic energy is the energy _____. in the nucleus of an atom of electrons and their shells in chemical bonds of elements and compounds

Answers

The correct statement to fill the blank would be the first option. Atomic energy is the energy in the nucleus of an atom of electrons and their shells. From the word atomic itself, we can say that this energy is energy within and carried by the atoms.

Answer:

in the nucleus of an atom

Explanation:

Which of the following molecules has correctly labeled bond dipoles?

Answers

Answer: The molecule identified with the letter C. HFO.


Explanation:


1) In covalent bonds, the dipolesare identified with an arrow pointing from the least electronegative element toward the most electronegative element.


2) The molecule HFO is formed by one covalent bond between H and O, and other covalent bond between F and O.


3) O is more electronegative than H, so in the H-O bond the dipole is identified with the arrow from the H atom toward the O atom. That is correctly indicated in the drawing C, in this way:


-|----→

H - O


4) F is more electronegative than O, so in the O-F bond the dipole is identified with an arrow from the O atom toward the F atom. That is correctly indicated in this way:


-|---→

O - F.

16.H2O (water) and NaCl (salt) are _________ that are in salt water, which is a(n) __________. Water and salt contain the ____________ hydrogen, oxygen, sodium, and chlorine. Compounds; mixture; elements
Mixture; compounds; elements
Element; compounds; mixture
Compound; elements; compounds

12.The number of _____ determines which element it is.

electrons
protons
positrons
neutrons

Answers

#1...Mixture; compounds; elements
#2...Protons 

How many electrons are in Al3+?

Answers

atomic number of aluminium  = 13
so the number of electrons=13
 aluminium cation, has 3 positive charge which it attains after losing 3 electrons (protons are not lost, there remain in the nucleus of the atom
electrons in Al3+ = 13 - 3 = 10 
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