Engineering Board Exam Reviewer · Chemistry · medium

What is the percentage of calcium by mass in CaCO₃? (Use H = 1, C = 12, N = 14, O = 16, Na = 23, S = 32, Cl = 35.5, Ca = 40)

  1. 12%
  2. 40%
  3. 48%
  4. 33%

Answer

B. 40%

Solution

%Ca = 40/100 × 100 = 40%.

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  1. What is the percentage by mass of oxygen in water? (Use H = 1, C = 12, N = 14, O = 16, Na = 23, S = 32, Cl = 35.5, Ca = 40)
  2. How many atoms are in 3 mol of helium?
  3. What is the mass of 0.25 mol of sodium hydroxide ( NaOH)? (Use H = 1, C = 12, N = 14, O = 16, Na = 23, S = 32, Cl = 35.5, Ca = 40)
  4. How many molecules are in 44 g of carbon dioxide? (Use H = 1, C = 12, N = 14, O = 16, Na = 23, S = 32, Cl = 35.5, Ca = 40)
  5. How many moles are there in 90 g of water? (Use H = 1, C = 12, N = 14, O = 16, Na = 23, S = 32, Cl = 35.5, Ca = 40)
  6. What is the molar mass of glucose, C6H12O6? (Use H = 1, C = 12, N = 14, O = 16, Na = 23, S = 32, Cl = 35.5, Ca = 40)
  7. What is the molar mass of calcium carbonate, CaCO₃? (Use H = 1, C = 12, N = 14, O = 16, Na = 23, S = 32, Cl = 35.5, Ca = 40)
  8. What is the molar mass of sulfuric acid, H2SO4? (Use H = 1, C = 12, N = 14, O = 16, Na = 23, S = 32, Cl = 35.5, Ca = 40)
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