Answer:
you did not show the options
Explanation:
The original mass of krypton 81 that is present in the ice is 6.70 grams.
<h3>How do we calculate original mass?</h3>
Original mass of any substance will be calculated as below for the decomposition reaction is:
N = N₀(1/2)ⁿ, where
N = remaining mass of krypton-81 = 1.675g
N₀ = original mass of krypton-81 = ?
n will be calculated as:
n = T/t, where
T = total time period = 458,000 years
t = half life time = 229,000 years
n = 458,000/229,000 = 2
Now putting all these values on the above equation, we get
N₀ = 1.675 / (1/2)²
N₀ = 6.70 g
Hence required mass is 6.70 g.
To know more about half life time, visit the below link:
brainly.com/question/2320811
The balanced chemical reaction is:
CH4 + 2O2 —> CO2 + 2H2O
You need to convert mass to moles (divide by molar mass):
CH4 moles = 5 / 16 = 0.31 mol
O2 moles = 5 / 32 = 0.16 mol
To figure out which reactant is limiting, divide the actual moles by the corresponding coefficient in the reaction:
CH4: 0.31 / 1 = 0.31
O2: 0.16 / 2 = 0.08
O2 is the lower number, so it is the limiting reactant. From the reaction we know it takes 2 moles of O2 to react with each mole of CH4. Therefore, for however many moles of O2 we actually have, half as many moles of CH4 will react. Since we have 0.16 mol of O2, only 0.08 mol of CH4 will react, leaving behind 0.31 - 0.08 = 0.23 mol of CH4.
Now convert back to mass (multiply by molar mass) to find the mass of CH4 remaining:
0.23 x 16 = 3.68g
The closest answer is B.
Answer:
<u>= 48.077 kcal </u>
Explanation:
The balanced equation is :
Since the stoichiometric coefficient of Na2O = 1 hence its heat is
<u>-120 Kcal/mol</u> rather -120 Kcal only.
This means when 1 mole of the Na2O is burned , then 120 kcal of energy is released .
Molar mass of Na2O = 2(mass of Na) + 1(mass of O)
= 2(22.98)+16
=61.97 gram/mol
Molar mass = mass of the substance in grams present in 1 mole of it.
In 1 mole of Na2O , 61.97 gram of it is present.
Hence
61.97 gram of Na2O = -120 Kcal of heat is released
1 gram of Na2O =
So,
24.8 gram of Na2O will produce,
= -48.077 kcal of heat
You can also proceed through mole concept:
Calculate number of moles in 24.8 gram Na2O
Moles of Na2O = 24.08/61.9 = 0.4007 moles
So these many moles will produces:
0.4007 x 120
=-48.07
The estimated population of the sea turtles for that location is 160 turtles
Let b represent the total turtles in the location.
<h3>Data obtained from the question</h3>
- Captured marked turtle = 15
The estimated turtles in sea can be obtained as follow:
Mark in sea / Total in sea = captured marked turtle / Captured turtle
40 / b = 15 / 60
Cross multiply
b × 15 = 40 × 60
b × 15 = 2400
Divide both side by 15
b = 2400 / 15
b = 160 turtles
Thus, the estimated turtles in the sea is 160 turtles
Learn more about estimation:
brainly.com/question/9583992
