Approximately when did the first plants and arthropods appear on land? A. 444 Ma B. 488 Ma C. 299 Ma D. 416 Ma

The strongest intermolecular interactions between hydrogen fluoride (hf) molecules arise from

According to the Bohr model of an atom, what happens when an electron moves from the second energy level to the third energy level and then back to the second energy level? Energy is absorbed and then stored in the atom.

In the reaction C + O2 → CO2, 18 g of carbon react with oxygen to produce 72 g of carbon dioxide. What mass of oxygen would be needed in the reaction? 18 g 54 g 72 g 90 g

Which stantment about temperatures in earths atmosphere is true Air temperature remains constant and all layers of earths atmosphere air temperature cannot be measured be on the troposphere Air temperature gets warmer as you move away from earth

Which of the following is typical of an endothermic reaction? The reaction container is warm. The reaction container is cold. Light is a product of the reaction. Sound is a product of the reaction.

What is the rough er connected to

Two students design an experiment to see if pushing or pulling a box across the floor is more effective. The first student pushes the box across the floor a distance of 20 feet and the second student times how long it takes.

15.00 g of NH4HS (s) is introduced into a 500. mL flask at 25 °C, the flask is sealed, and the system is allowed to reach equilibrium. What is the partial pressure of ammonia in this flask if Kp = 0.108 at 25 °C for: NH4HS (s) ⇄ NH3 (g) + H2S (g) ?

Among elements 1-18, which element or elements have the smallest effective nuclear charge if we use the equation zeff=z-s to calculate zeff? check all that apply.

Two clear solutions are placed in separate beakers. The first solution has a pH of 4, and the pH of the second solution is unknown. If the two solutions are mixed and the resulting pH is 5, the second solution must have