How many protons are in an element with an atomic number of 8 and a mass number of 18? question 5 options: 3 18 10 8

Answer : The number of protons in an element are 8.

Explanation :

Atomic number is defined as the number of protons or number of electrons.

Atomic number = number of protons = number of electrons

Mass number is defined as the sum of number of protons and number of neutrons.

Number of neutrons = Mass number - Number of protons

As we are given :

Atomic number of an element = 8

Mass number of an element = 18

Now we have to determine the number of protons for this element.

As, Atomic number = number of protons = number of electrons

So,

Atomic number = Number of protons = 8

Hence, the number of protons in an element are 8.

level 4 to level 2 : ))

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol