How many moles of atoms are contained in 4.0 g of calcium? [Ca = 40]
A0.05 mol
B0.10 molCORRECT
C0.20 mol
D0.40 mol
GCEChemistryStoichiometry and Mole Concept2020
AI
Toaster Teacher
Why the answer is B, and why the others tempt you.
Number of moles = mass ÷ molar mass = 4.0 ÷ 40 = 0.10 mol. Since calcium is a monatomic element, moles of atoms equals moles of the substance, which is 0.10 mol. The other options arise from arithmetic errors such as dividing incorrectly or multiplying instead of dividing.
Want this in Pidgin, Yoruba, Igbo or Hausa? Sign up free →
Practice more Chemistry questions
GCE Chemistry has thousands more questions like this — with Worked answers on every one.