Answer:
c. Boundary where air masses meet and cold air rises above warm air.
Explanation:
Half-life is the time taken for the concentration of the substance to reduce by 50%. The original sample of strontium had a mass of 1.6 gms. Thus, option d is correct.
<h3>What is half-life?</h3>
The half-life of any radioactive substance is the time period at which the concentration will get reduced to half the initial amount. The initial mass of Sr-90 is calculated as,
Given,
Quantity of the remaining substance N (t) = 0.40 gm
Initial radioactive substance quantity 
=?
Time duration (t) = 56 years
Half-life = 28 years
Substituting values above:
= 1.6 gm
Therefore, option d. the initial mass of Sr is 1.6 gm.
Learn more about half-life here:
brainly.com/question/16145921
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Answer:
pH ( potential Hydrogen ) is a negative logarithm of molar concentration of hydrogen ions.
![pH = - log[H {}^{ + } ]](https://tex.z-dn.net/?f=pH%20%3D%20%20-%20%20log%5BH%20%7B%7D%5E%7B%20%2B%20%7D%20%5D)
therefore:
Answer:
copper(ll) carbonate
Explanation:
Since the product is a salt which is copper(II) carbonate, water and carbon dioxide, this reaction is an acid + metal carbonate reaction.
Looking at the salt, Cu²⁺ has to be part of the reactants.
Hence, the missing compound there has to be copper(ll) carbonate, CuCO₃.
The balanced chemical equation would be:
CuCO₃ + 2HNO₃➙ Cu(NO₃)₂ +H₂O +CO₂
P.s. You left out CO₂ as a product in Q2 ;)
Just a recap of the main reactions you would've learnt:
1) Acid + base/ alkali ➙ salt + water
2) Acid + metal ➙ salt + hydrogen gas
3) Acid + metal carbonate ➙ salt + H₂O + CO₂
Atomic weight of an element can be calculated as follows:
average atomic weight =
(atomic weight of first isotope)(its percentage of abundance) +
(atomic weight of second isotope)(its percentage of abundance)
average atomic weight = 98.225 amu
atomic weight of first isotope = 97.780 amu
its percentage of abundance = 1 - 0.417 = 0.583
atomic weight of second isotope = ??
its percentage of abundance = 0.417
So, just substitute in the above equation to get the atomic weight of the second isotope as follows:
98.225 = (97.78)(0.583) + (mass2)(0.417)
atomic weight of second isotope = 98.847 amu
