An exponential decay law has the general form: A = Ao * e ^ (-kt) =>
A/Ao = e^(-kt)
Half-life time => A/Ao = 1/2, and t = 4.5 min
=> 1/2 = e^(-k*4.5) => ln(2) = 4.5k => k = ln(2) / 4.5 ≈ 0.154
Now replace the value of k, Ao = 28g and t = 7 min to find how many grams of Thalium-207 will remain:
A = Ao e ^ (-kt) = 28 g * e ^( -0.154 * 7) = 9.5 g
Answer 9.5 g.
Answer:
B
Explanation:
For solving this we need a heat balance

By changing the corresponding relations, we have

By cancelling similar factor, we obtain

Which means that the change of temperature in A is twice the change of B
Remember that a cation will be smaller than its neutral atom, and an anion will be larger than its neutral atom. This would automatically eliminate answer choices A and D.
Also keep in mind that atomic radii decreases from left to right as you move along a periodic table. It also decreases from bottom up.
Atomic radii increases as you move from right to left and as you go from up to down.
As bromine is higher up in the periodic table than Iodine, it would have a smaller radius. Iodine would have a larger radius.
The correct answer is B. Br
Answer:
6 moles of NaCl are needed to make 3.0 liters of a 2.0 M NaCl solution.
Explanation:
A 2M solution means that there are 2 moles of solute (NaCl in this case) in 1 liter of solution:
1 L solution-----2 moles of NaCl
3 L solution----x= (3 L solutionx2 moles of NaCl)/1 L solution= <em>6 moles of NaCl</em>