If 10.95 g K2SO4 is used up in a reaction, How many atoms would that be?

Answer / explanation :

To solve this problem, since we are given the number of grams, we can use this formula to calculate for number of mole

n = m / Mm

n - number of mole

m - number of mass

Mm - number of molar mass

Mm =

K - 39.0983

S - 28.0855

O - 15.999

K2SO4

Molar mass of K2SO4 = 39.0983 * 2 + 28.0855 + 15.999 * 4

Note : there are 2 atoms of K and 4 atoms of O, 1 atom of S in the compound

Mm = 78.1966 + 28.0855 + 63.996

= 170.2781g/mol

n = 10.95g/170.2781g/mol

= 0.0643mol

The number of atom = number of mole * the number of avogadros constant (6.023 * 10^23)

= 0.0643 * 6.023 * 10^23

= 3.873 * 10^22 atoms

3.79x10²² atoms K2SO4

Explanation: The solution to find the atoms of K2SO4 are as follows.

First find the moles of K2SO4.

10. 95 g K2SO4 x 1 mole K2SO4 / 174 g K2SO4

= 0.063 mole K2SO4

Next find the number of atoms using the Avogadro's number.

0.063 moles K2SO4 x 6.022x10 ²³ atoms K2SO4 / 1 mole K2SO4

= 3.79x10²² atoms K2SO4

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