Calcium hydride reacts with water to form calcium hydroxide and hydrogen gas. The balanced equation to this is #CaH_2+2H_2O#----#Ca(OH)_2+2H_2#
How many grams of calcium hydride are needed to form 8.400 g of hydrogen?

Question

Calcium hydride reacts with water to form calcium hydroxide and hydrogen gas.  The balanced equation to this is #CaH_2+2H_2O#----#Ca(OH)_2+2H_2#
How many grams of calcium hydride are needed to form 8.400 g of hydrogen?

Peyton Adams · Accepted Answer

You need #"87.69 g of CaH"_2# to form #"8.400 g of H"_2#.

There are four steps to answering this type of stoichiometry problem.

Write the balanced equation for the reaction.
Use the molar mass of #"H"_2# to convert grams of #"H"_2# to moles of #"H"_2#.
Use the molar ratio from the balanced equation to convert moles of #"H"_2# to moles of #"CaH"_2#.
Use the molar mass of #"CaH"_2# to convert moles of #"CaH"_2# to grams of #"CaH"_2#.
Step 1. Write the balanced equation.

#"CaH"_2 + "2H"_2"O" → "Ca(OH)"_2 + "2H"_2#
Step 2. Convert grams of #"H"_2# to moles of #"H"_2#.

The molar mass of #"H"_2# is 2.016 g/mol.

#8.400 cancel("g H"_2) × ("1 mol H"2)/(2.016 cancel("g H"2)) = "4.1667 mol H"_2#
Step 3. Use the molar ratio to calculate the moles of #"CaH"_2#.

From the balanced equation, the molar ratio is #"1 mol CaH"_2:"2 mol H"_2#.

#4.1667 cancel("mol H"_2) × ("1 mol CaH"_2)/(2 cancel("mol H"_2)) = "2.0833 mol CaH"_2#
Step 4. Convert moles of #"CaH"_2# to grams of #"CaH"_2#.

The molar mass of #"CaH"_2# is 42.09 g/mol.

#2.0833 cancel("mol CaH"_2) × ("42.09 g CaH"_2)/(1 cancel("mol CaH"_2)) = "87.69 g CaH"2#
The reaction requires #"87.69 g CaH"_2#.

This video link allows you to furthur practice similar problems.

Noah Aldrich · Answer

undefined To determine the grams of calcium hydride needed to form 8.400 g of hydrogen gas, we first need to find the molar mass of hydrogen gas (H2). Since 1 mole of hydrogen gas weighs 2 grams (2 atomic mass units for each hydrogen atom), the molar mass of H2 is 2 g/mol.

Next, we calculate the number of moles of hydrogen gas produced using the given mass:

Number of moles of H2 = mass of H2 / molar mass of H2
Number of moles of H2 = 8.400 g / 2 g/mol = 4.200 mol

According to the balanced chemical equation:
1 mole of CaH2 produces 2 moles of H2.

So, the number of moles of CaH2 needed is half the number of moles of H2 produced:

Number of moles of CaH2 = 4.200 mol / 2 = 2.100 mol

Finally, we find the mass of calcium hydride needed:

Mass of CaH2 = number of moles of CaH2 × molar mass of CaH2
Mass of CaH2 = 2.100 mol × (40.08 g/mol) ≈ 84.168 g

Therefore, approximately 84.168 grams of calcium hydride are needed to form 8.400 g of hydrogen gas.

Calcium hydride reacts with water to form calcium hydroxide and hydrogen gas. The balanced equation to this is #CaH_2+2H_2O#----#Ca(OH)_2+2H_2# How many grams of calcium hydride are needed to form 8.400 g of hydrogen?