An unknown gas effuses at a rate of 2.00 times the rate of Cl₂. What is the molar mass of the unknown gas?

Darla claims that the first periodic table developed by mendeleev was not completely accurate, so it is not useful at all. harmony argues that it establish the periodic table we use today, making it more credible. who is correct and why? darla is correct, because a model that has any mistakes should be thrown out. darla is correct, because a good model would not need to change. harmony is correct, because mendeleev’s model had all of the information correct in the first version. harmony is correct, because mendeleev’s model made predictions that came true.

Explanation for basic character?

The chart shows the bid provided by four contractors to complete a job. which contractor is the most cost-effective?