Answer:
If anything but H2O were found, it would be evidence of a chemical change. Therefore, 4 is the only viable evidence that it was a physical change of H2O liquid to H2O gas.
It is a trial aimed to reduce bias during an experiment. An example would be a sugar pill, something that has no real effect so that the results of the true trial can accurately be compared. Its like a control group.
Answer:
<span>In the addition of hbr to 1-butyne the electrophile in the first step of the mechanism is <u>Hydrogen atom of HBr</u>.
Explanation:
In this reaction first of all HBr approaches the triple bond. A Pi Complex (weak inter-molecular interactions) is formed between the two molecules. And the triple bond attacks the partial positive hydrogen atom creating a negative charge on Bromine along with positive charge on itself (Sigma Complex). In second step the negative Bromide attacks the positive carbon of Butyne.</span>
You take the grams of CO₂ times Avogadro's number divided by the molar mass.
