3. Which of these recorded observations is qualitative, rather than quantitative?

A chemical reaction is complete in 2.3 s.
The solid has a mass of 23.4 g.
The compound melts at 87.5°C.
Iron is denser than aluminum.
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D
Iron is denser than aluminum

Option D is qualitative data.

Iron is denser than aluminum.

Explanation:

Qualitative data:

The data which is measured without numerical values and describe only the qualities of substance is called qualitative data. For example,

The color of flame is red. It describe the quality of flame.

Sara is intelligent than her brother. It also describe the quality of Sara.

In given options, option D is qualitative data.

Iron is denser than aluminum.

Quantitative data:

The data which is measured in numerical values is called quantitative data. For example,

I have 1 dollar. It is quantitative data.

In given options, A,B,C shows quantitative data.

A chemical reaction is complete in 2.3 s.

The solid has a mass of 23.4 g.

The compound melts at 87.5°C.

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