Multiple Choice
How many milliliters of a 0.155 M KCl solution are required to contain 2.55 grams of KCl?
6. Chemical Quantities & Aqueous Reactions
Molarity
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How many grams of hydrazine, N2H4, must be added to a solvent to prepare 204 mL of a solution that is 0.42 M hydrazine?
A
2.10 grams
B
5.76 grams
C
8.64 grams
D
3.42 grams
Verified step by step guidance1
First, understand that molarity (M) is defined as moles of solute per liter of solution. The problem states that the solution is 0.42 M, meaning there are 0.42 moles of hydrazine (N2H4) per liter of solution.
Convert the volume of the solution from milliliters to liters. Since there are 1000 milliliters in a liter, divide 204 mL by 1000 to get the volume in liters.
Calculate the number of moles of hydrazine needed using the formula: \( \text{moles} = \text{molarity} \times \text{volume in liters} \). Substitute the values: molarity = 0.42 M and volume = 0.204 L.
Determine the molar mass of hydrazine (N2H4). Add the atomic masses of nitrogen and hydrogen: \( 2 \times 14.01 \text{ g/mol} + 4 \times 1.01 \text{ g/mol} \).
Finally, calculate the mass of hydrazine required using the formula: \( \text{mass} = \text{moles} \times \text{molar mass} \). Use the moles calculated in step 3 and the molar mass from step 4.
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