No atoms are lost or made during the chemical reaction so the total mass of the products is equal to the total mass of the reactants. In an atom, protons and neutrons contribute to the mass and since the number of them doesn’t change, the mass doesn’t either.


- <u>We </u><u>have </u><u>250g </u><u>of </u><u>liquid </u><u>water </u><u>and </u><u>it </u><u>needs </u><u>to </u><u>be </u><u>cool </u><u>at </u><u>temperature </u><u>from </u><u>1</u><u>0</u><u>0</u><u>°</u><u> </u><u>C </u><u>to </u><u>0</u><u>°</u><u> </u><u>C</u>
- <u>Specific </u><u>heat </u><u>of </u><u>water </u><u>is </u><u>4</u><u>.</u><u>1</u><u>8</u><u>0</u><u>J</u><u>/</u><u>g</u><u>°</u><u>C</u>

- <u>We </u><u>have </u><u>to </u><u>find </u><u>the</u><u> </u><u>total</u><u> </u><u>number </u><u>of </u><u>joules </u><u>released</u><u>. </u>

<u>We </u><u>know </u><u>that</u><u>, </u>
Amount of heat energy = mass * specific heat * change in temperature
<u>That </u><u>is, </u>

<u>Subsitute </u><u>the </u><u>required </u><u>values </u><u>in </u><u>the </u><u>above </u><u>formula </u><u>:</u><u>-</u>




Hence, 104,500 J of heat is released to cool 250 grams of liquid water from 100° C to 0° C.

<u>We </u><u>have </u><u>to </u><u>tell </u><u>whether </u><u>the </u><u>above </u><u>process </u><u>is </u><u>endothermic </u><u>or </u><u>exothermic </u><u>:</u><u>-</u>
Here, In the above process ΔT is negative and as a result of it Q is also negative that means above process is Exothermic
- <u>Exothermic </u><u>process </u><u>:</u><u>-</u><u> </u><u>It </u><u>is </u><u>the </u><u>process </u><u>in </u><u>which </u><u>heat </u><u>is </u><u>evolved </u><u>. </u>
- <u>Endothermic </u><u>process </u><u>:</u><u>-</u><u> </u><u>It </u><u>is </u><u>the </u><u>process </u><u>in </u><u>which </u><u>heat </u><u>is </u><u>absorbed </u><u>.</u>
The biological molecules that transport other substances are the proteins.
<h3>What are proteins?</h3>
Proteins are biological macromolecules that contains nitrogen in their molecules and are the building block of a living organism.
The proteins perform the following functions:
- they transport other substances,
- provide structural support,
- cause the movement of muscles, and
- catalyze chemical reactions in living organisms.
Learn more about protein here:
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<u>Answer:</u> The correct answer is 0.745 km
<u>Explanation:</u>
We are given:
A numerical value of 815 yards
To convert this into kilometers, we use the conversion factor:
1 km = 1093.6 yards
Converting the given value into kilometers, we get:

Hence, the correct answer is 0.745 km
61.24 is the molar mass of a gas which has a density of 0.00249 g/mL at 20.0 degrees celcius and 744.0 mm Hg.
Explanation:
given that:
density = 0.00249 g/ml (
) or 2.49 grams/litre
P = 744 mm Hg OR 0.978 atm
T = 20 Degrees or 293.15 Kelvin
R = 0.08206 Litre atm/mole K
molar mass =?
Formula used/
PV = nRT equation 1
here n is number of moles:
n = 
putting the value of n and value of density in the equation 1:
PV =
x RT
molar mass =
x 
= density x 
= 
= 61.24 is the molar mass of the gas.