객관식
How many grams of CuSO_4·5H_2O are required to prepare 25 mL of a 0.020 M stock solution?
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3. Chemical Reactions
Stoichiometry
객관식
What is the mass of NaCl required to prepare 140 grams of a 12% (by mass) NaCl solution in water?
A
28 grams
B
12 grams
C
127.2 grams
D
16.8 grams
검증된 단계별 안내1
Understand that a 12% (by mass) NaCl solution means 12 grams of NaCl are present in every 100 grams of solution.
Set up the relationship using the percentage by mass formula: \(\text{mass \%} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 100\).
Let the mass of NaCl be \(m\). Using the formula, write the equation: \(12 = \frac{m}{140} \times 100\).
Rearrange the equation to solve for \(m\): \(m = \frac{12 \times 140}{100}\).
Calculate \(m\) to find the mass of NaCl required to prepare 140 grams of a 12% NaCl solution.
