First, you need to find the number of moles of OH⁻ in a 250mL solution of 0.100M OH⁻. To do this, multiply 0.250L by 0.100M to get 0.025mol OH⁻. Then you use the fact that 1 mole of Sr(OH₂)·8H₂O contains 2 moles of OH⁻ which means that 0.0125mol of Sr(OH)₂·8H₂O contains 0.025mol OH⁻ (0.025/2=0.0125). Then to find the amount of Sr(OH)₂·8H₂O is needed you multiply its molar mass (265.76g/mol) by 0.0125mol to get 3.322g.
Therefore you need 3.322g of Sr(OH)₂·8H₂O.
I hope that helps. Let me know if anything is unclear.
Atomic structure and Isotopes Quiz - Quizizz. The mass number of an element that has 18 protons, 18 electrons, and 19 neutrons<span> is The atomic number of an element that has </span>9 protons<span>, 9 electrons, and </span>10 neutrons<span> is</span>
Answer:
63.5474U.M.A. es la masa atómica promedio del cobre
Explanation:
La masa atómica promedio de un átomo es definida como la suma de las masas de los isótopos multiplicada por su abundancia. Para el caso del cobre que tiene dos isótopos:
Cu = Masa 65Cu*Abundancia + Masa 63Cu*Abundancia
Reemplazando con los valores dados en el problema:
Cu = 62.9298U.M.A.*0.6909 + 64.9278U.M.A.*0.3091
Cu = 63.5474U.M.A. es la masa atómica promedio del cobre
Answer:
Atomic mass of Sodium is 22.9897 u. Note that, each element may contain more isotopes, therefore this resulting atomic mass is calculated from naturally-occuring isotopes and their abundance. The unit of measure for mass is the atomic mass unit (amu). One atomic mass unit is equal to 1.66 x 10 -24 grams.
Explanation:
They all have the same number of protons and electrons but differ in the number of neutrons because they are isotopes.