B.)<span>A doctor would use technetium-99m because a short half-life indicates a quick measurement, and a geologist would use rubidium-87 because a longer half-life means that there is a longer time to measure old rock. </span>
Answer:
1+
Explanation:
the number of protons tells you which element it is in the periodic table, you can notice that there is 1 less electron that then there is protons which means that the element had to give 1 electron away. When you get rid of 1 e- you have 1 proton more that electrons so that's why it's 1+
also the element is Cr
Answer:
13.92 %
Explanation:
Mass of 
= 12.5221 g
Molar mass of = 233.43 g/mol
The formula for the calculation of moles is shown below:
Thus,
Moles of = 0.0536 moles
According to the given reaction,
1 mole of is formed from 1 mole of 
Thus,
0.0536 moles of is formed from 0.0536 moles of
Moles of = 0.0536 moles
Moles of sulfur in 1 mole = 1 mole
Moles of sulfur in 0.0536 mole = 0.0536 mole
Molar mass of sulfur = 32.065 g/mol
Mass = Moles * Molar mass = 0.0536 * 32.065 g = 1.7187 g
Mass of ore = 12.3430 g
Mass % = 
= 
= 13.92 %
Answer:
Volume of N₂ = 14.76 L
Volume of H₂ = 29.52 L
Explanation:
Given data:
Mass of N₂H₄ formed = 28.5 g
Pressure = 1.50 atm
Temperature = 30°C (30+273 = 303 k)
Volume of N₂ and H₂ needed = ?
Solution:
Chemical equation:
N₂ + 2H₂ → N₂H₄
Number of moles of N₂H₄ formed = mass/ molar mass
Number of moles of N₂H₄ formed = 28.5 g/ 32 g/mol
Number of moles of N₂H₄ formed = 0.89 mol
Now we will compare the moles of N₂H₄ with N₂ and H₂ form balance chemical equation.
N₂H₄ : N₂
1 : 1
0.89 : 0.89
N₂H₄ : H₂
1 : 2
0.89 : 2×0.89 = 1.78 mol
Volume of H₂:
PV = nRT
1.50 atm × V = 1.78 mol × 0.0821 atm.L/mol.K × 303 K
V = 44.28atm.L /1.50 atm
V = 29.52 L
Volume of N₂:
PV = nRT
1.50 atm × V = 0.89 mol × 0.0821 atm.L/mol.K × 303 K
V = 22.14 atm.L /1.50 atm
V = 14.76 L
