How many moles of urea are present in 5.4 g ? (Molar mass = 60)
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When dividing decimals by multiples of 10, temporarily scale up the numerator ($54 / 6 = 9$) and shift the decimal point back to save time and prevent arithmetic mistakes.
Step 1: Understanding the Question:
Given the mass and molar mass of urea, the objective is to compute the equivalent number of moles.
Step 2: Key Formula or Approach:
The foundational mole calculation formula is: Number of moles (n) = Given Mass (m) / Molar Mass (M).
Step 3: Detailed Explanation:
Given mass of urea m = 5.4 g, and M = 60 g/mol. Substituting into the formula yields n = 5.4 / 60. This simplifies as n = (54 × 10⁻¹) / 60 = 0.9 × 10⁻¹ = 0.09 moles.
Step 4: Final Answer:
The quantity of urea is 0.09 moles, corresponding to option (B).