Which of the following describes a response to external stimuli ?
a. a boy sneezes when exposed to a cat dander.
b. a girl eats food when she is hungry.
c. a child becomes hyperactive do to a chemical imbalance.
d. a person yawns when oxygen levels in the blood are low.

219 grams of iron (iii) oxide reacts with excess carbon according to the reaction equation shown below. fe2o3 + c → fe + co2 after a scientist performs the chemical reaction they find the actual yield of iron to be 57.4 grams. calculate the percent yield of this chemical reaction.

Determine the percent sulfuric acid by mass of a 1.61 m aqueous solution of h2so4. %

Given sno2 + 2h2 - sn + 2h20 tin oxide reacts with hydrogen to produce tin and water. how many moles of sno2 are needed to produce 500.0 grams of sn?