The answer is 40.
We can solve this by finding out the number of protons, and neutrons. Atomic number of an element means the number of protons in that element. So, the atom has 30 protons if the atomic number is 30.
On the other hand, mass number is the total number of protons and neutrons, but not electrons, because they're too light comparing to the other 2. Therefore, we can simply solve the number of neutrons in the atom by subtracting the number of protons from the mass number. 70 - 30 = 40.
Therfore, the number of neutrons is 40.
Examples that have been believed to be science: such as religion, flat earth, etc.
The partial pressure of oxygen given the total barometric pressure is : 108.15 mmHg
<u>Given data : </u>
Total barometric pressure = 515 mmHg
Assuming oxygen percentage = 21%
Barometric pressure dry at 37°C
<h3 /><h3>Determine the partial pressure of oxygen </h3>
Applying the relation below
Partial pressure = oxygen percentage * Barometric pressure
= 21% * 515 mmHg
= 108.15 mmHg
Hence we can conclude that the partial pressure of oxygen is 108.15 mmHg.
Learn more about Partial pressure : brainly.com/question/1835226
Answer: 19.4 g/cm3
Explanation: density is the relationship between mass over volume.
So density of gold is 15.7g/0.81cm3 = 19.4 g/cm3
