Answer:
P₄ + 5O₂ → 2P₂O₅
Explanation:
Phosphorus burn in the presence of air and produced diphosphorus pentoxide.
Chemical equation:
P₄ + O₂ → P₂O₅
Balanced chemical equation:
P₄ + 5O₂ → 2P₂O₅
Equation is balanced because there are four phosphorus atoms ans ten oxygen atoms in both side of equation.
Coefficient with reactant and product:
P₄ 1
O₂ 5
P₂O₅ 2
First read the introduction.
Seconds look at the pictures how to build it.
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>
Answer:
mass number = protons + neutrons.
Explanation:
Together, the number of protons and the number of neutrons determine an element's mass number: mass number = protons + neutrons. If you want to calculate how many neutrons an atom has, you can simply subtract the number of protons, or atomic number, from the mass number.