Can someone link me videos and sites that can teach me the formula to solve these? Or try to help me understand how to solve these?
1.You have 200g of a radioisotope . If the half-life of this radioisotope is 20 days, how many grams will remain after 40 days?
2.Calculate the molarity of a saline solution prepared by dissolving 19.3g of sodium chloride in 250 mL of water.
3.Calculate the pH of a solution that has [OH-]=1x10^-9
1. You need no website. If half is gone after 20 days, then after 40 days, half of half is all that remains: 1/4*200=50g
2. Molarity= mass/molmass * 1/volumeinLiters
= 19.3/formalamassNaCl * 1/4
formula mass Na=23+35 check that.
3. pH+pOH=14
pOH=-log(OH)=-log (10^-9)=9
PH=14-9=5
"Samantha,"
You are cheating on your chemistry final. Please review the INCA honor code which you are clearly violating. Sadly, you are only cheating yourself because the goal of school is to become educated. If you are going on to college, your college will expect you to know this information when you get there.
1. To solve this question, you can use the formula for exponential decay:
N(t) = N(0) * (1/2)^t/h
where:
- N(t) is the amount of the substance remaining after time t
- N(0) is the initial amount of the substance
- t is the elapsed time
- h is the half-life of the substance
In this case, N(0) is 200g, t is 40 days, and h is 20 days. Plugging these values into the formula, we get:
N(40) = 200 * (1/2)^(40/20)
Simplifying the equation, we have:
N(40) = 200 * (1/2)^2
N(40) = 200 * (1/4)
N(40) = 50g
Therefore, after 40 days, 50 grams of the radioisotope will remain.
To find videos and sites that can teach you more about exponential decay and how to solve these types of problems, you can search for terms such as "radioactive decay formula explained" or "half-life calculation tutorial" on platforms like YouTube or educational websites.
2. To calculate the molarity of a solution, you need to use the formula:
Molarity (M) = moles of solute / volume of solution (in liters)
In this case, you are given the mass of the solute (19.3g of sodium chloride) and the volume of the solution (250 mL of water, which is equivalent to 0.25 liters).
First, you need to convert the mass of sodium chloride to moles. To do this, you can use the molar mass of sodium chloride, which is 58.44 g/mol. Divide the mass of sodium chloride (19.3g) by its molar mass to get the moles:
moles = mass / molar mass
moles = 19.3g / 58.44 g/mol
moles ≈ 0.331 mol
Now, you can substitute the moles of solute (0.331 mol) and the volume of solution (0.25 L) into the molarity formula:
M = 0.331 mol / 0.25 L
M ≈ 1.324 M
The molarity of the saline solution prepared by dissolving 19.3g of sodium chloride in 250 mL of water is approximately 1.324 M.
To further understand the concept of molarity and how to calculate it, you can search for videos or websites that explain "molarity calculation" or "molarity explained."
3. To calculate the pH of a solution based on the concentration of hydroxide ions (\[OH^-\]), you can use the equation:
\[pH= -\log_{10}[OH^-]\]
In this case, you are given \[OH^-\] = 1x10^-9.
Plugging this value into the equation, we have:
\[pH= -\log_{10}(1x10^-9)\]
Simplifying the equation, we get:
\[pH= -\log_{10}(10^-9)\]
Using the property of logarithms, we know that \[log_{10}(10^-9) = -9\]. Therefore:
\[pH= 9\]
The pH of the solution with a concentration of hydroxide ions \[OH^-\] = 1x10^-9 is 9.
To find videos and sites that can teach you more about pH and how to calculate it, you can search for terms like "pH calculation explained" or "pH scale tutorial" on platforms like YouTube or educational websites.