Answer:
52 da
Step-by-step explanation:
Whenever a question asks you, "How long to reach a certain concentration?" or something similar, you must use the appropriate integrated rate law expression.
The i<em>ntegrated rate law for a first-order reaction </em>is
ln([A₀]/[A] ) = kt
Data:
[A]₀ = 750 mg
[A] = 68 mg
t_ ½ = 15 da
Step 1. Calculate the value of the rate constant.
t_½ = ln2/k Multiply each side by k
kt_½ = ln2 Divide each side by t_½
k = ln2/t_½
= ln2/15
= 0.0462 da⁻¹
Step 2. Calculate the time
ln(750/68) = 0.0462t
ln11.0 = 0.0462t
2.40 = 0.0462t Divide each side by 0.0462
t = 52 da
Answer:
pH of buffer =4.75
Explanation:
The pH of buffer solution is calculated using Henderson Hassalbalch's equation:
![pH=pKa+log[\frac{[salt]}{[acid]}](https://tex.z-dn.net/?f=pH%3DpKa%2Blog%5B%5Cfrac%7B%5Bsalt%5D%7D%7B%5Bacid%5D%7D)
Given:
pKa = 3.75
concentration of acid = concentration of formic acid = 1 M
concentration of salt = concentration of sodium formate = 10 M
![pH=3.75+log[\frac{10}{1}]=3.75+1=4.75](https://tex.z-dn.net/?f=pH%3D3.75%2Blog%5B%5Cfrac%7B10%7D%7B1%7D%5D%3D3.75%2B1%3D4.75)
pH of buffer =4.75
You convert kinetic energy into thermal energy when you rub two sticks together.
Nuclear fusion in the sun involves hydrogen (H) atoms
combining to form helium (He). A student claims that since the atmosphere
contains hydrogen, any fusion reaction on Earth would result in an uncontrolled
chain reaction. What is wrong in the student’s reasoning is that the uncontrolled
chain reactions can only happen during nuclear fission.
