CaH2 is so reactive with water that it can be used to "dry" solvents other than water. If a sample if solvent that contains a total of 14g of water is added to 24.6g of calcium hydride, which of these will remain after the reaction is complete: water or calcium hydride?
A. CaH2 will be left over
B. water will be left over
C. these two will both be used up completely
D. there is no way to predict
write the balanced equation:
CaH2 + 2H20>> Ca(OH)2+ 2H2
So there are two moles of water for each mole of calcium hydride. Now figure the masses and see how much of each you have.
If you have more than twice the moles of water, water will be left over.
See both answers given to the question below:
http://www.jiskha.com/display.cgi?id=1254688201
i got the mm of CaH2 to be 42.096 and the two moles of H2O to be 36.032. This means that CaH2 will be left over correct?
To determine which substance will remain after the reaction is complete, we need to compare the amounts of water and calcium hydride.
First, let's calculate the molar masses of water (H2O) and calcium hydride (CaH2):
- Molar mass of H2O = 2(1.008 g/mol) + 16.00 g/mol = 18.016 g/mol
- Molar mass of CaH2 = 40.08 g/mol + 2(1.008 g/mol) = 42.090 g/mol
Next, we can calculate the number of moles of each substance:
- Moles of water = Mass of water / Molar mass of water = 14g / 18.016 g/mol ≈ 0.776 mol
- Moles of calcium hydride = Mass of calcium hydride / Molar mass of calcium hydride = 24.6g / 42.090 g/mol ≈ 0.584 mol
According to the equation for the reaction of calcium hydride with water:
CaH2 + 2H2O → Ca(OH)2 + 2H2
From the balanced chemical equation, we can see that the stoichiometric ratio between calcium hydride and water is 1:2. This means that for every 1 mole of calcium hydride, 2 moles of water are required for a complete reaction.
The moles of water (0.776 mol) are more than double the moles of calcium hydride (0.584 mol). Therefore, we can conclude that calcium hydride will be completely consumed during the reaction, while some water will remain.
Therefore, the correct answer is:
B. Water will be left over.