객관식
If a chemical reaction starts with 20 g of reactants and proceeds to completion with no side reactions, what is the maximum mass of products that can be formed according to the law of conservation of mass?
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3. Chemical Reactions
Stoichiometry
객관식
How many grams of NH_3 are needed to provide the same number of molecules as in 0.15 g of SF_6?
A
0.21 g
B
0.082 g
C
0.15 g
D
0.032 g
검증된 단계별 안내1
Calculate the number of moles of SF_6 in 0.15 g by using its molar mass. The molar mass of SF_6 is calculated by summing the atomic masses: sulfur (S) is approximately 32.07 g/mol and fluorine (F) is approximately 18.998 g/mol. So, molar mass of SF_6 = 32.07 + 6 \(\times\) 18.998.
Use the formula for moles: \(\text{moles} = \frac{\text{mass}}{\text{molar mass}}\). Substitute the mass of SF_6 (0.15 g) and its molar mass to find the moles of SF_6.
Since the problem asks for the amount of NH_3 that has the same number of molecules, recall that the number of molecules is proportional to the number of moles. Therefore, the moles of NH_3 needed are equal to the moles of SF_6 calculated.
Calculate the molar mass of NH_3 by adding the atomic masses: nitrogen (N) is approximately 14.01 g/mol and hydrogen (H) is approximately 1.008 g/mol. So, molar mass of NH_3 = 14.01 + 3 \(\times\) 1.008.
Finally, calculate the mass of NH_3 needed using the formula \(\text{mass} = \text{moles} \times \text{molar mass}\). Use the moles found in step 3 and the molar mass from step 4 to find the mass of NH_3 that contains the same number of molecules as 0.15 g of SF_6.
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