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3 years ago

Which statement about exothermic reactions are true?

Chemistry

1 answer:

Hatshy [7]3 years ago

7 0

Answer:

It is either the third or fourth statement.

Explanation:

This is because exothermic reactions give off heat.

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Write the number in scientific nation form

Yuri [45]

Answer:

its already in scientific notation form however its ordinary or real form is -0.005682

Explanation:

scientific notation

when a number is expressed with some power of 10 multiplied by a number between 1 to 10 is called scientific notation

4 0

3 years ago

If you start a chemical reaction with 5 atoms of hydrogen, how many hydrogen atoms will you have when it is finished? Group of a

mote1985 [20]

Answer:

5 atoms

Explanation:

According to the law of conservation of mass, "matter is neither created nor destroyed in the cause of a chemical reaction".

We finish with what we start with in a chemical reaction. Although new species might form, the number of atoms on both sides of the expression will still be maintained.

All chemical reactions obey this law of conservation.

8 0

3 years ago

What expression approximates the volume of O2 consumed, measure at STP, when 55 g of Al reacts completely with excess O2?2 Al(s)

nikdorinn [45]

Answer : The volume of $O_2$ consumed are, $0.75\times 2\times 22.4$ L.

Explanation :

The balanced chemical reaction will be:

$4Al(s)+3O_2(g)\rightarrow 2Al_2O_3(s)$

First we have to calculate the moles of Al.

$\text{Moles of }Al=\frac{\text{Mass of }Al}{\text{Molar mass of }Al}$

Molar mass of Al = 27 g/mole

$\text{Moles of }Al=\frac{55g}{27g/mol}=2mole$

Now we have to calculate the moles of $O_2$ .

From the reaction we conclude that,

As, 4 mole of Al react with 3 moles of $O_2$

So, 2 mole of Al react with $\frac{3}{4}\times 2=0.75\times 2$ moles of $O_2$

Now we have to calculate the volume of $O_2$ consumed.

As we know that, 1 mole of substance occupies 22.4 liter volume of gas.

As, 1 mole of $O_2$ occupies 22.4 liter volume of $O_2$ gas

So, $0.75\times 2$ mole of $O_2$ occupies $0.75\times 2\times 22.4$ liter volume of $O_2$ gas

Therefore, the volume of $O_2$ consumed are, $0.75\times 2\times 22.4$ L.

3 0

3 years ago

Problem Page Question It takes to break a carbon-carbon single bond. Calculate the maximum wavelength of light for which a carbo

Marizza181 [45]

This is a incomplete question. The complete question is:

It takes 348 kJ/mol to break a carbon-carbon single bond. Calculate the maximum wavelength of light for which a carbon-carbon single bond could be broken by absorbing a single photon. Round your answer to correct number of significant digits

Answer: 344 nm

Explanation:

$E=\frac{Nhc}{\lambda}$