4. your older brother announces that the lid to a jar of pickles from the refrigerator

is "impossible" to loosen. you take the jar, hold the lid under the hot water from

your sink's faucet for a few seconds, and calmly open the jar. your brother, when

faced with this blow to his pride, claims that he loosened it for you. what

knowledge of materials have you applied in this situation that really explains

how you were able to open the lid?

Explanation:

As the pickle jar was placed inside the refrigerator so, due to the decrease in temperature of the refrigerator the lid faced contraction in size.

As a result, it became tightly fitted over the mouth of the jar.

But when the lid was held under the hot water from your sink's faucet for a few seconds, then it undergoes a thermal expansion.

As a result, size of lid expanded as compared to the size of mouth of the jar. Hence, the lid is able to be opened up.

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

percent abundance for cu-63 can be shown as:

63 x + 65 (1-x) = 62.9296

65 - 62.9296 = 2 x

x = 1.035

thus, percent abundance for cu-63 is 1.035

percent abundance for cu-65 can be shown as:

63 x + 65 (1-x) = 64.9278

65 - 64.9278 = 2 x

x = 0.0361

thus, percent abundance for cu-63 is 0.0361

the mass spectrum of cu-63 showing the intense peak as, this isotope is found in nature more abundantly around 92.38 % in comparison to cu-65 which is found 62.58 % naturally