HardChemistryHigh School (9–10)GeneralAtoms and Molecules › Laws of Chemical CombinationNumericalConceptual
A student sparks 9 g of hydrogen with 56 g of oxygen to make water.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A student sparks of hydrogen with of oxygen to make water. Hydrogen and oxygen join in the ratio by mass. How much water is made? Which gas is left over, and how much of it?
Need a reminder? The key ideaShow
A compound always has its elements in the same ratio by mass: water , carbon dioxide , ammonia , magnesium oxide . To share a mass in a ratio, add the parts first. Any extra of one element is left over.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Hydrogen needed. . There is , so the oxygen runs out first.
Step 2. Water. .
Step 3. Left over. of hydrogen.
Answer: of water, with of hydrogen left over.
Check. , the same as .
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