Answer:
4 g after 58.2 years
0.0156 After 291 years
Explanation:
Given data:
Half-life of strontium-90 = 29.1 years
Initially present: 16g
mass present after 58.2 years =?
Mass present after 291 years =?
Solution:
Formula:
how much mass remains =1/ 2n (original mass) ……… (1)
Where “n” is the number of half lives
to find n
For 58.2 years
n = 58.2 years /29.1 years
n= 2
or 291 years
n = 291 years /29.1 years
n= 10
Put values in equation (1)
Mass after 58.2 years
mass remains =1/ 22 (16g)
mass remains =1/ 4 (16g)
mass remains = 4g
Mass after 58.2 years
mass remains =1/ 210 (16g)
mass remains =1/ 1024 (16g)
mass remains = 0.0156g
Answer:
There are 2.5 * 10^22 beryllium atoms in 0.37 grams
Explanation:
Step 1: Data given
The mass of an atom of beryllium is 1.5 x 10^-26 kg.
Total mass = 0.37 grams
Step 2: Calculate number of atoms
1 atom = 1.5 * 10 ^-26 kg
X atoms = 0.00037 kg
X = 0.00037/1.5*10^-26
X = 2.467 * 10^22 atoms ≈ 2.5 * 10^22 atoms
There are 2.5 * 10^22 beryllium atoms in 0.37 grams
Answer : The rate law for formation of NOBr based on this mechanism is, ![\frac{k_1\times k_2}{k_1^-}[Br_2][NO]^2](https://tex.z-dn.net/?f=%5Cfrac%7Bk_1%5Ctimes%20k_2%7D%7Bk_1%5E-%7D%5BBr_2%5D%5BNO%5D%5E2)
Explanation :
The overall reaction is:

Rate law = ![k[Br_2][NO]^2](https://tex.z-dn.net/?f=k%5BBr_2%5D%5BNO%5D%5E2)
The first step of the overall reaction is:


Rate law 1 = ![k_1[Br_2][NO]](https://tex.z-dn.net/?f=k_1%5BBr_2%5D%5BNO%5D)
Rate law 2 = ![k_1^-[NOBr_2]](https://tex.z-dn.net/?f=k_1%5E-%5BNOBr_2%5D)
The second step of the overall reaction is:

Rate law 3 = ![k_2[NOBr_2][NO]](https://tex.z-dn.net/?f=k_2%5BNOBr_2%5D%5BNO%5D)
Now rate law of overall reaction can be obtained as follows.
We are multiplying rate law 1 and rate law 3 and dividing by rate law 2, we get:
Rate law = ![\frac{[k_1[Br_2][NO]]\times [k_2[NOBr_2][NO]]}{[k_1^-[NOBr_2]]}](https://tex.z-dn.net/?f=%5Cfrac%7B%5Bk_1%5BBr_2%5D%5BNO%5D%5D%5Ctimes%20%5Bk_2%5BNOBr_2%5D%5BNO%5D%5D%7D%7B%5Bk_1%5E-%5BNOBr_2%5D%5D%7D)
Rate law = ![\frac{k_1\times k_2}{k_1^-}[Br_2][NO]^2](https://tex.z-dn.net/?f=%5Cfrac%7Bk_1%5Ctimes%20k_2%7D%7Bk_1%5E-%7D%5BBr_2%5D%5BNO%5D%5E2)
Rate law = ![k[Br_2][NO]^2](https://tex.z-dn.net/?f=k%5BBr_2%5D%5BNO%5D%5E2)
The rate law for formation of NOBr based on this mechanism is, ![\frac{k_1\times k_2}{k_1^-}[Br_2][NO]^2](https://tex.z-dn.net/?f=%5Cfrac%7Bk_1%5Ctimes%20k_2%7D%7Bk_1%5E-%7D%5BBr_2%5D%5BNO%5D%5E2)
Answer: Testing the electrical conductivity of an aqueous solution of the substance is the correct option.
Explanation:
An ionic substance is defined as the substance formed due to transfer of electrons(s) from one atom to another of the combining species.
For example, when a metal and a non-metal chemical combines then an electron will always be transferred from the metal to the non-metal.
Hence, a metal and non-metal always form an ionic bond.
It is known that water is a polar substance and polar or ionic substances readily dissolve in it.
So, when an ionic compound is dissolved in water then it will dissociate into ions. And, as electricity is the flow of ions or electrons hence, an aqueous solution of ionic substance is able to conduct electricity.
But an ionic compound in crystal form will not be able to conduct electricity because then ions are not present in free state.
Thus, we can conclude that testing the electrical conductivity of an aqueous solution of the substance, would be most useful in providing data to determine if the substance is an ionic compound.
Answer:
D
Explanation:
Because if I said its 35 degrees outside that has nothing to do with climate maybe if I said its usually 35 degrees in the month of December but just saying what temperature it doesn't tell you anything about climate
Well, the definition of climate is the weather conditions prevailing in an area in general or over a long period so I don't really know
So maybe it is d