Element A has a half-life of 10 days. A scientist measures out 200 g of this substance. After 30 days has passed, the scientist
2 answers:
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Answer : The final temperature of the mixture is
Explanation :
In this problem we assumed that heat given by the hot body is equal to the heat taken by the cold body.
And as we know that,
Mass = Density × Volume
Thus, the formula becomes,
where,
= specific heat of ethanol =
= specific heat of water =
= mass of ethanol
= mass of water
= density of ethanol = 0.789 g/mL
= density of water = 1.0 g/mL
= volume of ethanol = 45.0 mL
= volume of water = 45.0 mL
= final temperature of mixture = ?
= initial temperature of ethanol =
= initial temperature of water =
Now put all the given values in the above formula, we get
Therefore, the final temperature of the mixture is
25.9 kJ/mol. (3 sig. fig. as in the heat capacity.)
<h3>Explanation</h3>The process:
.
How many moles of this process?
Relative atomic mass from a modern periodic table:
- K: 39.098;
- N: 14.007;
- O: 15.999.
Molar mass of :
.
Number of moles of the process = Number of moles of dissolved:
.
What's the enthalpy change of this process?
for
. By convention, the enthalpy change
measures the energy change for each mole of a process.
.
The heat capacity is the least accurate number in these calculation. It comes with three significant figures. As a result, round the final result to three significant figures. However, make sure you keep at least one additional figure to minimize the risk of rounding errors during the calculation.
Answer:
pH of buffer =4.75
Explanation:
The pH of buffer solution is calculated using Henderson Hassalbalch's equation:
Given:
pKa = 3.75
concentration of acid = concentration of formic acid = 1 M
concentration of salt = concentration of sodium formate = 10 M
pH of buffer =4.75