Question

answer the questions based on the data from the video lab.

1. for every unit of oxygen collected, how many units of hydrogen gas were collected?
2. what is the balanced equation for the burning of hydrogen in oxygen?
3. what is the reverse equation of the burning of hydrogen in oxygen?
4. in the electrolysis apparatus, where do the hydrogen ions go?
5. based on your observations of the electrolysis apparatus, where do the oxide ions go?
6. what is the mathematical ratio of the volume of oxygen created to the volume of hydrogen created?
7. how does the mathematical ratio translate to relative amounts expressed in the balanced equation?

Explanation:

1. From the electrolysis of water (the basis of the video lab), the volume ratio of hydrogen to oxygen produced is 2:1.
2. The burning of hydrogen in oxygen produces water; balance by adjusting coefficients to match atom counts.
3. The reverse of hydrogen combustion is the decomposition of water, which occurs via electrolysis.
4. In electrolysis of water, hydrogen ions ($H^+$) migrate to the negative cathode, gain electrons, and form hydrogen gas.
5. In electrolysis of water, oxide ions (or hydroxide ions, $OH^-$) migrate to the positive anode, lose electrons, and form oxygen gas.
6. Experimental observations from water electrolysis show 2 volumes of hydrogen are produced for every 1 volume of oxygen.
7. The volume ratio directly corresponds to the mole ratio of reactants/products in the balanced chemical equation, as equal volumes of gases (at same T/P) have equal moles.

Answer:

1. 2 units of hydrogen gas
2. $2H_2(g) + O_2(g)

ightarrow 2H_2O(l)$

1. $2H_2O(l)

ightarrow 2H_2(g) + O_2(g)$ (electrolysis of water)

1. Hydrogen ions move to the cathode (negative electrode), where they are reduced to form hydrogen gas.
2. Oxide/hydroxide ions move to the anode (positive electrode), where they are oxidized to form oxygen gas.
3. 1:2 (oxygen volume to hydrogen volume)
4. The 1:2 volume ratio translates to a 1:2 mole ratio of $O_2$ to $H_2$, which is reflected in the coefficients of the balanced equation for water formation/electrolysis.