<u>Given:</u>
Mass of solvent water = 4.50 kg
Freezing point of the solution = -11 C
Freezing point depression constant = 1.86 C/m
<u>To determine:</u>
Moles of methanol to be added
<u>Explanation:</u>
The freezing point depression ΔTf is related to the molality m through the constant kf, as follows:
ΔTf = kf*m
where ΔTf = Freezing point of pure solvent (water) - Freezing pt of solution
ΔTf = 0 C - (-11.0 C) = 11.0 C
m = molality = moles of methanol/kg of water = moles of methanol/4.50 kg
11.0 = 1.86 * moles of methanol/4.50
moles of methanol = 26.613 moles
Ans: Thus around 26.6 moles of methanol should be added to 4.50 kg of water.
The chemical equation without coefficients is:
Ca + CO2 + O2 --------> Ca CO3
You can balance that equation by trial an error.
This is the chemical equation balanced:
2Ca + 2CO2 + O2 --------> 2Ca CO3
Count the atoms on each side to check the balance
Atom Left side right side
Ca 2 2
C 2 2
O 2*2 + 2 = 6 2*3 = 6
Then those are the coefficients:
a0 = 2
a1 = 2
a2 = 1
a3 = 2
Answer : The time passed in years is 
Explanation :
Half-life = 5730 years
First we have to calculate the rate constant, we use the formula :
Now we have to calculate the time passed.
Expression for rate law for first order kinetics is given by:
where,
k = rate constant = 
t = time passed by the sample = ?
a = let initial amount of the reactant = X g
a - x = amount left after decay process = 
Now put all the given values in above equation, we get
Therefore, the time passed in years is
m = mass of the truck traveling = 2500 kg
v = speed of the truck traveling = 75 km/h = 75 (km/h) (1000 m/ 1 km) (1 h /3600 sec) = 20.83 m/s
h = plank's constant = 6.63 x 10⁻³⁴
λ = wavelength of truck = ?
according to de broglie's principle, wavelength of truck is given as
λ = h/(mv)
inserting the values in the above equation
λ = (6.63 x 10⁻³⁴)/((2500) (20.83))
λ = 1.3 x 10⁻³⁸ m
