3.01 Ă— 10^24 Ă— (12/5) hydrogen atoms
Looking at the formula for the molecule, the ratio of carbon to hydrogen atoms is 5:12, so if we divide the number of carbon atoms by 5 and then multiply by 12, we can find the number of hydrogen atoms. Let's look at the available options and see what makes sense.
3.01 Ă— 10^24 Ă— (12/5) hydrogen atoms
* This is exactly correct.
(3.01 Ă— 10^24 / 5) hydrogen atoms
* Nope. This will tell you how many pentane MOLECULES you have, but not the number of hydrogen atoms.
3.01 Ă— 10^24 Ă— (5/12) hydrogen atoms
* Close, but the ratio (5/12) will tell you the number of carbon atoms you have if you give it the number of hydrogen atoms. So this choice is wrong.
3.01 Ă— 10^24 Ă— 12 hydrogen atoms description
* This would tell you the number of hydrogen atoms you have if you know the number of pentane molecules you have. So this choice is also wrong.
The answer is 7.33 g.
<span>To calculate this, we will use the the ideal gas law:
PV = nRT
where
P - pressure of the gas,
V - volume of the gas,
n - amount of substance of gas,
R - gas constant,
T - temperature of the gas.</span>
Since the amount of substance of gas (n) can be expressed as mass (m) divided by molar mass (M), then:
PV = RTm/M
It is given:
P = 0.98 atm
V = 10.2 l
T = 26°C = 299.15 K
R = 0.082 l atm/Kmol (gas constant)
M (H2O) = 2Ar(H) + Ar(O) = 2*1 + 16 = 2 + 16 = 18g
m = ?
Since PV = RTm/M, then:
m = PVM/RT
m = 0.98 · 10.2 · 18 / 0.082 · 299.15 = 179.928/24.5303 = 7.33 g
Answer : The correct option is (A).
Explanation :
- Endothermic reaction : When two liquids are combine into a flask, then the flask feels cold when we touch it because the system absorbed heat from the surrounding.
In general, endothermic process absorbs heat and cool the surrounding.
- Exothermic reaction : When two liquids are combine into a flask, then the flask feels hot when we touch it because the system released heat into the surrounding.
In general, exothermic process releases heat and rise the temperature of surrounding.
72.0726 is the percent for carbon