Answer:
Quantity remaining= 27.5 grams
Step-by-step explanation:
If the initial quantity of the radioactive isotope= 220 grams
And for each half life it will reduce to half of its original quantity
For first half life
Quantity= 220/2
Quantity= 110 grams
Now for the second half life , the quantity to work with will be 110 grams
Second half life
Quantity= 110/2
Quantity= 55 grams
For the third half life , the quantity to work with is 55 grams
Third half life
Quantity= 55/2
Quantity= 27.5 grams
So after 3 half life's of this radioactive isotope, the amount remaining out of 220 = 27.5 grams.
Another simple way to do this
Since half life reduce the isotope by half of its original.
The third half life will reduce it by (1/2)^3= 1/8
So the quantity remaining= 1/8*220
Quantity remaining= 27.5 grams
Answer:
A. -205.7 kJ
Step-by-step explanation:
The overall enthalpy of reaction be calculated when the intermediate steps are present
formed in a multi-step process.
Answer:
y=2/5x+3/5
Step-by-step explanation:
Use the slope formula to get the slope:
m=4/10
m=2/5
The y intercept is 3/5
The equation is y=2/5x+3/5
Answer:
- <u>120 pens and 200 pencils.</u>
<u></u>
Explanation:
You can set a system of two equations.
<u>1. Variables</u>
<u />
- x: number of pens
- y: number of pencils
<u>2. Cost</u>
- <em>each pen costs</em> $1, then x pens costs: x
- <em>each pencil costs</em> $0.5, then y pencil costs: 0.5y
- Then, the total cost is: x + 0.5y
- The cost of the whole purchase was $ 220, then the first equation is:
x + 0.5y = 220 ↔ equation (1)
<u>3. </u><em><u>There were 80 more pencils than pens</u></em>
Then:
pencils = 80 + pens
↓ ↓
y = 80 + x ↔ equation (2)
<u>4. Solve the system</u>
i) Substitute the equation (2) into the equation (1):
ii) Solve
iii) Substitute x = 120 into the equation (2)
Solution: 120 pens and 200 pencils ← answer
Seriously nobody knows the anwser?? Im done ill just fail
