Astatine -211 has half a life of seven hours. If u start with 50.0 grams of astatine-211, how much will remain after 28 hours
1 answer:
Answer:
3.125 grams
Explanation:
Applying,
R = ()R'............... Equation 1
Where R = Original mass of Astatine-211, R' = mass of Astatine-211 left after decay, t = total disintegeration time, n = halflife of Astatine-211
make R' the subject of the equation
R' = R/()............ Equation 2
From the question,
Given: R = 50 grams, t = 28 hours, n = 7 hours
Substitute into equation 2
R' = 50/()
R' = 50/(2⁴)
R' = 50/16
R' = 3.125 grams
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Answer:
Explanation:
Since we are given the mass, specific heat, and temperature, we should use the following formula for heat energy.
The mass of the aluminum is 26.3 grams. Its specific heat is 0.930 Joules per gram degree Celsius. We need to find the change in temperature.
- The change in temperature is the difference between the initial temperature to the final temperature.
- The temperature changes <em>from</em> 23.0°C <em>to</em> 67.0°C, so the initial is 23 degrees and the final is 67 degrees.
- ΔT= final temperature - initial temperature
- ΔT= 67°C - 23°C
- ΔT= 44°C
Now we know all the values.
- m= 26.3 g
- c= 0.930 J/g °C
- ΔT= 44°C
Substitute the values into the formula.
Multiply the first two numbers together. The units of grams cancel.
Multiply again. This time, the units of degrees Celsius cancel.
<u>1076.196 Joules</u> of heat will be absorbed by the piece of aluminum.
Number of moles of HCl = 
=
= 0.763 mole
From balanced equation:
4 moles of HCl give 2 moles Cl2
0.763 mole HCl give ?? mole Cl2
by cross multiplication :
= 0.38 mole Cl2
mass of Cl2 = moles x molar mass = 0.38 x 70.9 = 27 g
=
From balanced equation:
4 moles of HCl give 2 moles Cl2
0.763 mole HCl give ?? mole Cl2
by cross multiplication :
= 0.38 mole Cl2
mass of Cl2 = moles x molar mass = 0.38 x 70.9 = 27 g