Answer:
64.52 mg.
Explanation:
The following data were obtained from the question:
Half life (t½) = 1590 years
Initial amount (N₀) = 100 mg
Time (t) = 1000 years.
Final amount (N) =.?
Next, we shall determine the rate constant (K).
This is illustrated below:
Half life (t½) = 1590 years
Rate/decay constant (K) =?
K = 0.693 / t½
K = 0.693/1590
K = 4.36×10¯⁴ / year.
Finally, we shall determine the amount that will remain after 1000 years as follow:
Half life (t½) = 1590 years
Initial amount (N₀) = 100 mg
Time (t) = 1000 years.
Rate constant = 4.36×10¯⁴ / year.
Final amount (N) =.?
Log (N₀/N) = kt/2.3
Log (100/N) = 4.36×10¯⁴ × 1000/2.3
Log (100/N) = 0.436/2.3
Log (100/N) = 0.1896
Take the antilog
100/N = antilog (0.1896)
100/N = 1.55
Cross multiply
N x 1.55 = 100
Divide both side by 1.55
N = 100/1.55
N = 64.52 mg
Therefore, the amount that remained after 1000 years is 64.52 mg
Answer:
4.26 %
Explanation:
There is some info missing. I think this is the original question.
<em>Calculate the percent ionization of nitrous acid in a solution that is 0.249 M in nitrous acid. The acid dissociation constant of nitrous acid is 4.50 × 10
⁻⁴.</em>
<em />
Step 1: Given data
Initial concentration of the acid (Ca): 0.249 M
Acid dissociation constant (Ka): 4.50 × 10
⁻⁴
Step 2: Write the ionization reaction for nitrous acid
HNO₂(aq) ⇒ H⁺(aq) + NO₂⁻(aq)
Step 3: Calculate the concentration of nitrite in the equilibrium ([A⁻])
We will use the following expression.
![[A^{-} ] = \sqrt{Ca \times Ka } = \sqrt{0.249 \times 4.50 \times 10^{-4} } = 0.0106 M](https://tex.z-dn.net/?f=%5BA%5E%7B-%7D%20%5D%20%3D%20%5Csqrt%7BCa%20%5Ctimes%20Ka%20%7D%20%3D%20%5Csqrt%7B0.249%20%5Ctimes%204.50%20%5Ctimes%2010%5E%7B-4%7D%20%20%7D%20%3D%200.0106%20M)
Step 4: Calculate the percent ionization of nitrous acid
We will use the following expression.
![\alpha = \frac{[A^{-} ]}{[HA]} \times 100\% = \frac{0.0106M}{0.249} \times 100\% = 4.26\%](https://tex.z-dn.net/?f=%5Calpha%20%3D%20%5Cfrac%7B%5BA%5E%7B-%7D%20%5D%7D%7B%5BHA%5D%7D%20%5Ctimes%20100%5C%25%20%3D%20%5Cfrac%7B0.0106M%7D%7B0.249%7D%20%5Ctimes%20100%5C%25%20%3D%204.26%5C%25)
You must add 75 mL water to 195 mL 90 % alcohol to make 270 mL of 65 % alcohol.
<em>Step 1.</em> Calculate the volume of 90 % alcohol needed
You can use the dilution formula
<em>V</em>1×<em>C</em>1 = <em>V</em>2×<em>C</em>2
where
<em>V</em>1 and<em> V</em>2 are the volumes of the two solutions
<em>C</em>1 and <em>C</em>2 are the concentrations
You can solve the above formula to get
<em>V</em>2 = <em>V</em>1 × <em>C</em>1/<em>C</em>2
<em>V</em>1 = 270 mL; <em>C</em>1 = 65 %
V2 = ?; _____<em>C</em>2 = 90 %
∴<em>V</em>2 = 270 mL × (65 %/90 %) = 195 mL
You need 195 mL of 90 % alcohol to make 270 mL of 65 % RA
<em>Step 2</em>. Calculate the amount of water to add.
Volume of water = 270 mL – 195 mL = 75 mL
If there is no net force on an object, then the object will <span>maintain it's rate of speed. Basically, net force is the change in an object's motion. If it is stationary and not moving, the object will stay stationary. If the object is moving at a rate of 2 miles per hour, it will constantly continue to move 2 mph because there is no net force.</span>
An Ionic bond is the result of transfer of electrons between atoms
