Need !
select the choice that best completes the following sentence.

simple machines
a.
are tools that make work easier.
b.
reduce the amount of energy needed to do work.
c.
are made up of multiple moving parts.
d.
cannot be combined to make compound machines.

Calculate the enthalpy of the following reaction: 4 b (s) + 3 o2 (g) → 2 b2o3 (s) given the following pertinent information: (a) b2o3 (s) + 3 h2o (g) → 3 o2 (g) + b2h6 (g), δhoa = +2035 kj (b) 2 b (s) + 3 h2 (g) → b2h6 (g), δhob = +36 kj (c) h2 (g) + latex: \frac{1}{2} 1 2 o2 (g) → h2o (l), δhoc = −285 kj (d) h2o (l) → h2o (g), δhod = +44 kj

Calculate the molar mass of aluminum oxide (al2o3). express your answer to four significant figures.

What effect does a decrease in temperature have on the overall rate of a chemical reaction? a decrease in temperature decreases . the reaction rate will