What is the mass of 2.01 x 10^23 atoms of lead?

Mass = 68.376 g

Explanation:

Given data:

Mass of lead = ?

Number of atoms of lead = 2.01 ×10²³ atom

Solution:

Number of moles of lead:

1 mole of lead contain 6.022×10²³ atom

2.01 ×10²³ atom × 1 mol /6.022×10²³ atom

0.33 mol

Mass of lead:

Mass = number of moles ×  molar mass

Mass = 0.33 mol ×  207.2 g/mol

Mass = 68.376 g

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