Answer:
B. topsoil is made entirely of decomposed organic remains
Answer:
The given compound cannot be cocaine.
Explanation:
The chemist can comment on the nature of compound being cocaine or not from the depression in freezing point.
Depression in freezing point of is related to molality as:
Depression in freezing point = Kf X molality
Where
Kf = cryoscopic constant = 4.90°C/m
depression in freezing point = normal freezing point - freezing point of solution
depression in freezing point = 5.5-3.9 = 1.6°C
1.6°C = 4.90 X molality
![molality=\frac{1.6}{4.90} = 0.327 m](https://tex.z-dn.net/?f=molality%3D%5Cfrac%7B1.6%7D%7B4.90%7D%20%3D%200.327%20m)
we know that:
![molality=\frac{moles}{mass of solvent(kg)}=\frac{moles}{0.008kg}](https://tex.z-dn.net/?f=molality%3D%5Cfrac%7Bmoles%7D%7Bmass%20of%20solvent%28kg%29%7D%3D%5Cfrac%7Bmoles%7D%7B0.008kg%7D)
therefore
moles = 0.327X0.008 = 0.00261 mol
![moles=\frac{mass}{molarmass}](https://tex.z-dn.net/?f=moles%3D%5Cfrac%7Bmass%7D%7Bmolarmass%7D)
![molarmass=\frac{mass}{moles}=\frac{0.50}{0.00261}= 191.57g/mol](https://tex.z-dn.net/?f=molarmass%3D%5Cfrac%7Bmass%7D%7Bmoles%7D%3D%5Cfrac%7B0.50%7D%7B0.00261%7D%3D%20191.57g%2Fmol)
The molar mass of cocaine is 303.353
So the given compound cannot be cocaine.
Answer:
0.082 M
Explanation:
First we calculate the moles of KOH added, by multiplying its volume and concentration:
- 0.22 M * 16 mL = 3.52 mmol KOH
Given that <em>one mole of acid reacts with one mole of base</em>, in the lactic acid sample there were 3.52 acid moles as well.
Finally we divide the acid moles by the volume, to calculate the concentration:
- 3.52 acid moles / 43 mL = 0.082 M
Answer:
New pressure P2 = 4.95 atm
Explanation:
Given:
Old volume V1 = 1.50 L
New volume V2 = 0.50 L
Old pressure P1 = 1.65 atm
Find:
New pressure P2
Computation:
P1V1 = P2V2
So,
(1.50)(1.65) = (0.50)(P2)
New pressure P2 = 4.95 atm
To solve this, we simply equate the change in enthalpy for
the two substances since heat gained by water is equal to heat lost of aluminum.
We know that the heat capacity of aluminum is 0.089 J/g°C and that of water is
4.184 J/g°C. Therefore:
450.2 (95.2 - T) (0.089) = 60 (T – 10) (4.184)
3,814.45456 – 40.0678 T = 251.04 T – 2,510.4
291.1078 T = 6,324.85456
<span>T = 21.7°C</span>