Molecular Mass

Rosie was asked to calculate the mass of Mg(OH)₂.

She said add the atomic mass of oxygen, hydrogen, and magnesium together.

What is the ERROR in her thinking?

• Rosie forgot to multiply by the coefficient.

• Rosie forgot to ADD the subscripts of each element inside the parentheses with the subscript outside the parentheses.

• Rosie forgot to MULTIPLY the subscripts of each element inside the parentheses with the subscript outside the parentheses.

• Rosie forgot about an element in the chemical formula.

Tags

NGSS.MS-PS1-1

Calculate the mass of Fe₃(PO₄)₂.

• 358 amu

• 294 amu

• 389 amu

• 401 amu

Calculate the the mass of (NH₄)CO₃.

• 78 amu

• 94 amu

• 120 amu

• 110 amu

Calculate the mass of 3(ClF)₂.

• 108 amu

• 216 amu

• 324 amu

• 320 amu

Tags

NGSS.HS-PS1-7

Calculate the mass of 2CH₃COOH.

• 60 amu

• 120 amu

• 118 amu.

• 106 amu

Tags

NGSS.HS-PS1-7

Calculate the mass of 2Ga₂(SO₃)₃.

• 380 amu.

• 284 amu

• 760 amu

• 696 amu

Molecular mass of NH3 is

Tags

NGSS.MS-PS1-1

Molecular mass of aluminium chloride is

Molecular mass of aluminium sulphite is

Molecular mass of NaCl is _____ .

• 58.5 u

• 59.25 u

• 52 u

• 25 u

Answer explanation

Molecular mass of sodium = 23 u Molecular mass of Chlorine = 35.5 u Total mass of 1 mole = 23 +35.5 = 58.5 u