Multiple Choice
What is the enthalpy change associated with the reaction of 25.0 g of SO2 in excess oxygen, given the reaction: 2 SO2(g) + O2(g) → 2 SO3(g) with ΔH° = -198.2 kJ?
3. Chemical Reactions
Stoichiometry
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What volume of 0.128 M HCl is needed to completely neutralize 2.87 g of Mg(OH)₂?
A
0.750 L
B
0.250 L
C
0.350 L
D
0.500 L
Verified step by step guidance1
First, determine the molar mass of Mg(OH)₂. The molar mass is calculated by adding the atomic masses of magnesium (Mg), oxygen (O), and hydrogen (H). The formula is Mg(OH)₂, which consists of one Mg atom, two O atoms, and two H atoms.
Calculate the number of moles of Mg(OH)₂ using the formula: \( \text{moles} = \frac{\text{mass}}{\text{molar mass}} \). Use the given mass of Mg(OH)₂, which is 2.87 g, and the molar mass calculated in the previous step.
Write the balanced chemical equation for the neutralization reaction between HCl and Mg(OH)₂: \( \text{Mg(OH)}_2 + 2\text{HCl} \rightarrow \text{MgCl}_2 + 2\text{H}_2\text{O} \). This equation shows that 1 mole of Mg(OH)₂ reacts with 2 moles of HCl.
Using the stoichiometry from the balanced equation, calculate the moles of HCl required to neutralize the moles of Mg(OH)₂. Since 1 mole of Mg(OH)₂ requires 2 moles of HCl, multiply the moles of Mg(OH)₂ by 2 to find the moles of HCl needed.
Finally, calculate the volume of 0.128 M HCl solution required using the formula: \( \text{volume} = \frac{\text{moles of HCl}}{\text{concentration of HCl}} \). Use the moles of HCl calculated in the previous step and the given concentration of HCl, which is 0.128 M.
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