The rate of reaction that can be measured in the dark by determining the amount of oxygen gas consumed in a period of time is the rate of respiration.
Why?
Plants can undergo two types of reactions involving oxygen:
- <u>Photosynthesis: </u>In this type of reaction, plants use energy from light to synthesize glucose. The chemical reaction for photosynthesis is: 6H₂O + 6CO₂ → C₆H₁₂O₆ + 6O₂, and this reaction produces oxygen gas in the presence of light, that means that to measure the rate of photsynthesis, you'll need to measure the amount of oxgen gas <u>produced</u> in a period of time.
- <u>Respiration:</u> In this type of reaction, plants convert the energy stored in the chemical bonds of molecules such as glucose to obtain energy. The chemical reaction for respiration is: C₆H₁₂O + 6O₂ → 6H₂O + 6CO₂, since this reaction consumes oxygen gas in the dark, that means that to measure the rate of respiration, you'll need to measure the amount of oxygen gas <u>consumed</u> in a period of time.
Have a nice day!
Chemical change<span> is any change that results in the formation of new chemical substances. At the molecular level, chemical change involves making or breaking of bonds between atoms. These changes are chemical:</span>
<span>iron rusting (iron oxide forms)gasoline burning (water vapor and carbon dioxide form)eggs cooking (fluid protein molecules uncoil and crosslink to form a network)bread rising (yeast converts carbohydrates into carbon dioxide gas)milk souring (sour-tasting lactic acid is produced)suntanning (vitamin D and melanin is produced)</span>
Physical change rearranges molecules but doesn't affect their internal structures. Some examples of physical change are:
<span>whipping egg whites (air is forced into the fluid, but no new substance is produced)magnetizing a compass needle (there is realignment of groups ("domains") of iron atoms, but no real change within the iron atoms themselves).<span>boiling water (water molecules are forced away from each other when the liquid changes to vapor, but the molecules are still H2O.)</span>dissolving sugar in water (sugar molecules are dispersed within the water, but the individual sugar molecules are unchanged.)dicing potatoes (cutting usually separates molecules without changing them.)</span>
Classification of real processes can be tricky. Complex changes can be broken down into many simpler steps. Some of the steps are chemical and others are physical, so the overall process can't cleanly be placed in either category. For example, boiling coffee involves chemical change (the delicate molecules that give coffee its flavor react with air and become new, bitter-tasting substances) and physical change (the water in the coffee is going from liquid to gaseous form.)
By use of ideal gas equation PV= nRT where n is the number of moles,P = pressure, V = volume, R= gas constant (0.08206 L. atm/ mol.k) ant T is the temperature,
to calculate the number of moles(n) =PV/RT
convert ml to L, that is 200/1000= 0.2 L
convert mmHg to atm, that is 780mm hg x 1atm/ 760 mm hg= 1.026 atm
convert temperature to kelvin, that is 135 +273= 408 k
n is therefore= (0.2 x 1.026)/ ( 0.08206 x 408)= 6.129 x10^-3 moles
from avogadro constant 1moles = 6.02 x10^23 molecules what about 6 .129 x10^-3 moles
= ( 6.02 x10^23) x (6.129 x10^-3)/ 1mole = 3.69 x10^21 molecules
Answer:
16:1
Explanation:
Atoms of element X weigh 32 times more than atoms of element Y. We can write this in a symbolic way.
mX = 32 mY [1]
where,
- mX and mY are the masses of X and Y, respectively
A compound has the formula: XY₂, that is, in 1 molecule of XY₂ there is 1 atom of X and 2 atoms of Y. The ratio of the mass of X to the mass of Y in this compound equals:
mX/2 mY [2]
If we substitute [1] in [2], we get:
mX/2 mY = 32 mY/2 mY = 16 = 16:1
