When must scientist conduct controlled experiments?

It requires 24 hours for a sample of helium gas to effuse through a porous membrane. How long will it take for the same amount of oxygen gas to effuse through the same membrane? Assume both gases are at the same temperature. A. 12 hours B.

Which class of compounds is responsible for the scents and flavors of many fruits? A. amides B. amines C. ethers D. esters

Calculate the mass of water produced when 42.0 g of propane, c3h8, is burned with 115 g of oxygen. hint: write balanced equation first

4.887x10^23 atom of Ne to moles

Aqueous potassium bromide reacts with aqueous silver nitrate AgNO3 to form aqueous potassium nitrate KNO3 and solid silver bromide. Write a balanced chemical equation for this reaction.

Hemoglobin, the oxygen-carrying protein in red blood cells, has four iron atoms per molecules ad contains 0.340 percent iron by mass. calculate the molar mass of hemoglobin

Nancy wants to find out how the steepness of a hill's slope affects the amount of soil that erodes from it. She has soil, a long pan, and a pile of books with which to build a model hillside. She has a watering can to model rainfall.

Elements on the periodic table are arranged by increasing?

What is the difference between molecular formula and molecular model

The average kinetic energy of the atoms that make up a substance which is changing from a liquid to a solid is