Which of the following is NOT a pure substance? A. milk B. oxygen C. water D. carbon dioxide

2 answers:

4 0

Among the choices given, the substance that is not considered pure is C. milk. Milk is not pure because it is composed of more than one kind of molecule. Milk is composed of lactic acid, water, etc which is a combination of different molecules to form the solution. Others are only made up of one kind of molecule

Sav [38]3 years ago

3 0

Milk is not a pure substance. It is a mixture of many substances in a solution.

I hope this helps. Let me know if anything is unclear.

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About 3% of the water on Earth is freshwater. Only about 40% of that freshwater is available for human use. Why is so much fresh

Ilya [14]

I believe the answer you're looking for is B. It's Polluted. I hope this helps.

3 0

2 years ago

Read 2 more answers

The question is in the picture below

Rus_ich [418]

Answer:

$\Delta\text{H}_1+2\Delta\text{H}_2-\Delta\text{H}_3$

Explanation:

Hess's Law of Constant Heat Summation states that if a chemical equation can be written as the sum of several other chemical equations, the enthalpy change of the first chemical equation is equal to the sum of the enthalpy changes of the other chemical equations. Thus, the reaction that involves the conversion of reactant A to B, for example, has the same enthalpy change even if you convert A to C, before converting it to B. Regardless of how many steps it takes for the reactant to be converted to the product, the enthalpy change of the overall reaction is constant.

With Hess's Law in mind, let's see how A can be converted to 2C +E.

$\bf{\text{A} \rightarrow 2\text{B}}$ (Δ $\text{H}_1$ ) -----(1)

Since we have 2B, multiply the whole of II. by 2:

$\bf{2\text{B} \rightarrow 2\text{C} +2\text{D}}$ (2Δ $\text{H}_2$ ) -----(2)

This step converts all the B intermediates to 2C +2D. This means that the overall reaction at this stage is $\text{A} \rightarrow 2\text{C} +2\text{D}$ .

Reversing III. gives us a negative enthalpy change as such:

$\bf{2\text{D} \rightarrow \text{E}}$ (-Δ $\text{H}_3$ ) -----(3)

This step converts all the D intermediates formed from step (2) to E. This results in the overall equation of $\text{A} \rightarrow 2\text{C} +\text{E}$ , which is also the equation of interest.