Which of the following statements is the most accurate about the trends in atomic radii? a. Atomic radii increase with increasing atomic number across a period, but do not change in a column.
b. Atomic radii decrease with increasing atomic number across a period, but decease with increasing atomic number down a group.
c. Atomic radii decrease with increasing atomic number from left to right across a period, but increase with increasing atomic number down a group.
d. Atomic radii decrease with increasing atomic number across a period, but do not change in a group

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.

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