<u>Answer:</u> The final temperature of the coffee is 43.9°C
<u>Explanation:</u>
To calculate the final temperature, we use the equation:

where,
q = heat released = 
m = mass of water = 10.0 grams
C = specific heat capacity of water = 4.184 J/g°C
= final temperature = ?
= initial temperature = 20°C
Putting values in above equation, we get:

Hence, the final temperature of the coffee is 43.9°C
It would be 4.2, hope this helps.
Answer:

Explanation:
Hello!
In this case, when we want to balance chemical reactions such as in this case, the idea is to equal to number of atoms of each element at each side of the equation according to the lay of conservation of mass, just as shown below:

Because we have four phosphorous and ten oxygen atoms at each side.
Best regards!
<h2>Natural Abundance for 10B is 19.60%</h2>
Explanation:
- The natural isotopic abundance of 10B is 19.60%.
- The natural isotopic abundance of 11B is 80.40%.
- The isotopic masses of boron are 10.0129 u and 11.009 u respectively.
For calculation of abundance of both the isotopes -
Supposing it was 50/50, the average mass would be 10.5, so to increase the mass we need a more percentage of 11.
Determining it as an equation -
10x + 11y= 10.8
x+y=1 (ratio)
10x + 10y = 10
By taking the denominator away from the numerator
we get;
y = 0.8
x + y = 1
∴ x = 0.2
To get percentages we need to multiply it by 100
So, the calculated abundance is 80% for 11 B and 20% 10 B.