Answer:
the layer of a liquid or gaseous heat-transfer agent between the free stream and a heat-exchange surface. In this layer the temperature of the heat-transfer agent changes from that of the wall to that of the free stream
Explanation:
The answer is 1/8.
Half-life is the time required for the amount of a sample to half its value.
To calculate this, we will use the following formulas:
1.

,
where:
<span>n - a number of half-lives
</span>x - a remained fraction of a sample
2.

where:
<span>

- half-life
</span>t - <span>total time elapsed
</span><span>n - a number of half-lives
</span>
The half-life of Sr-90 is 28.8 years.
So, we know:
t = 87.3 years
<span>

= 28.8 years
We need:
n = ?
x = ?
</span>
We could first use the second equation, to calculate n:
<span>If:

,
</span>Then:

⇒

⇒

<span>⇒ n ≈ 3
</span>
Now we can use the first equation to calculate the remained amount of the sample.
<span>

</span>⇒

⇒

<span>
</span>
The titrant for this exercise. suppose Ca(OH)₂ were used as the titrant, instead of NaOH. This will make the titrant twice as concentrated in hydroxide ion. the analyte will still be HC₂H₃O₂. the stoichiometry ratio of HC₂H₃O₂ to Ca(OH)₂ is 1 : 2.
The balanced reaction of the given condition as follow :
Ca(OH)₂ + 2HC₂H₃O₂ ------> Ca(C₂H₃O₂)₂ + 2H₂O
from the equation it is clear that stoichiometry of Ca(OH)₂ is 1 and the stoichiometry of HC₂H₃O₂ is 2. therefore the stoichiometry ratio of HC₂H₃O₂ to Ca(OH)₂ is 1 : 2.
Thus, The titrant for this exercise. suppose Ca(OH)₂ were used as the titrant, instead of NaOH. This will make the titrant twice as concentrated in hydroxide ion. the analyte will still be HC₂H₃O₂. the stoichiometry ratio of HC₂H₃O₂ to Ca(OH)₂ is 1 : 2.
To learn more about stoichiometry here
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