Answer:
Explanation: The lowest pressure in a laboratory is 4.0×10^-11Pa
Using Ideal gas equation
PV = nRT
P= 4.0×10^-11Pa
V= 0.020m^3
T= 20+273= 293k
n=number of moles = m/A
Where m is the number of molecules and A is the Avogradro's number=6.02×10²³/mol
R=8.314J/(mol × K)
PV= m/A(RT)
4.0×10^-11 ×0.020 = m/6.02×10²³(8.314×293)
m = 4.0×10^-11×0.020×6.02×10^23 / (8.314×293)
m = 1.98×10^8 molecules
Therefore,the number of molecules is 1.98×10^8
Answer:
See below!
Explanation:
For the chemical formula, you need to have enough of each atom so that the charge is zero.
Aluminum has a +3 charge, and fluorine has a -1 charge. Since the charge has to be zero, you need three fluorines, giving you AlF₃.
Barium has a +2 charge, and oxygen has a -2 charge. Since the charges are equal in magnitude but opposite in sign, you only need one of each atom giving you BaO.
The name of the ionic compound will be the metal and then the nonmetal. When putting the nonmetal in, change the ending to "-ide". For example "chlorine" would be "chloride.
CaCl₂ ==> calcium chloride
Ga₂S₃ ==> gallium sulfide
K₃N ==> potassium nitride
AlF₃ ==> aluminum fluoride
BaO ==> barium oxide
Since Lutetium-177 is a beta and gamma emitter, the daughter nuclide produced from the decay of this radioisotope is 177Hf.
Beta emission of a radioisotope yields a daughter nuclide whose amass number is the same as that of its parent nucleus but its atomic number is greater is greater than that of the parent nucleus by 1 unit.
Also, gamma emission does not lead to any change in the mass number of atomic number of the daughter nucleus produced.
Hence, the stable daughter nuclide, 177Hf is produced.
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Scientists repeat experiments for reliability. Experiments have to be repeated, since performing an experiment only once, does not prove a scientists theory on the experiment, which they develop by performing the experiment. And then performing the experiment again or even many times to prove or disapprove their theories. Btw, before an experiment begins, the scientist will make a hypothesis of what they believe will happen. If proven correctly, they would then use those results they record throughout the experiment, from beginning to end to prove whether or not their hypothesis are correct or incorrect. Click to let others know, how helpful is it
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So that they can prove the other scientists views wrong and develop a new theory in which there is more sense and credibility.
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BASICALLY, I THINK THE ANSWER IS 1 OR 2 OR
