The atomic mass of Europium is 152 amu
Work:
151(0.4803) = 72.52 amu
153(0.5197) = 79.5 amu
72.5 + 79.5 = 152 amu
Answer:
A. there is an isotope of lanthanum with an atomic mass of 138.9
Explanation:
By knowing the different atomic masses of both Lanthanum atoms, we can not tell anything about their occurence in nature. Therefore, all the last three options are incorrect. Because, the atomic mass does not tell anything about the availability or natural abundance of an element.
Now, the isotopes of an element are those elements, which have same number of electrons and protons as the original element, but different number of neutrons. Therefore, they have same atomic number but, different atomic weight or atomic masses.
Hence, by looking at an elements having same atomic number, but different atomic masses, we can identify them as isotopes.
Thus, the correct option is:
<u>A. there is an isotope of lanthanum with an atomic mass of 138.9.</u>
Answer:Sugar
Explanation:Things being dissolved are solutes and things doing the dissolving are the solutions. So Sugar is being dissolved by water which makes sugar the solute.
Answer: To solve this question, we need to use the Avogadro's Number, which is a constant first discovered by Amadeo Avogadro, an Italian scientist. He discovered that in a mole of a substance, there are 6,02*10²³ molecules. Using this relationship, we apply the following conversion factor:
So, 8,50 * 10²⁴ molecules of Na₂SO₃ represent 14,12 moles of Na₂SO₃
Explanation:
NaBr + CaF2 → NaF + CaBr2 What coefficients are needed to balance the chemical equation? A) 1,1,1,1 B) 1,2,1,2 C) 1,2,2,1 D) 2,1
elena-s [515]
D.
2NaBr + CaF2 --> 2NaF + CaBr2 gives you:
2Na 2Na
2Br 2F
1Ca 1Ca
2F 2Br
This is balanced.
