Explanation
To find the molar mass of K2Cr2O7 are needed the atomic masses of each element that the molecule contains.
(Please, the periodic table is useful)
The atomic masses:
K) 39.0
Cr) 52.0
O) 16.0
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The molar mass = 2 x 39.0 (K) + 2 x 52.0 (Cr) + 7 x 16.0 (O) = 294 g/mol
Answer: A. 294 g/mol
