Formaldehyde has the formula ch2o. how many molecules are there in 0.11 g of formaldehyde

 2.21 x molecule

To answer this question, you need to know the formaldehyde molecular mass.
Formaldehyde molecular weight would be 12+ 1(2) + 16= 30 g/mol
After knowing the molecular mass you can count how many molecules by multiplying it by Avogadro's number. The calculation would be:
0.11g / (30g/mol) x 6.022140857 × = 0.02208 x = 2.21 x  

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