Question

when two substances were combined, bubbles were produced and the temperature dropped. this most likely means that
a a chemical reaction took place
b the two substances had low boiling points
c one substance dissolved in the other
d the two substances are non - reactive
question 8
hydrogen and oxygen react to produce water. which of the following is the correctly balanced chemical equation for this reaction?
a h₂ + o₂ = h₂o
b 2h₂ + o₂ = 2h₂o
c h₂ + o₂ = h₂o₂
d 3h₂ + 2o₂ = 3h₂o

Explanation:

1. For the first question, when two substances are combined and the temperature drops, it is an endothermic reaction. Endothermic reactions absorb heat from the surroundings, causing a temperature decrease.
2. For the second question, the balanced chemical - equation for the reaction between hydrogen and oxygen to form water is \(2H_2 + O_2

ightarrow2H_2O\). This is because we need to balance the number of hydrogen and oxygen atoms on both sides of the equation. On the left - hand side, 2 moles of \(H_2\) give 4 hydrogen atoms and 1 mole of \(O_2\) gives 2 oxygen atoms. On the right - hand side, 2 moles of \(H_2O\) also have 4 hydrogen atoms and 2 oxygen atoms.

Answer:

1. A chemical reaction took place (assuming the temperature drop is due to an endothermic chemical reaction).
2. B. \(2H_2 + O_2

ightarrow2H_2O\)