How many significant figures are in the number 4.0070 x 1012?

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4

Explanation: -

The number of significant figures in 4.0070 is 5.

The number of significant figures in 1012 is 4.

So during multiplication of significant figures, the number of significant figures in answer would be the smaller value 4.

4.0070 x 1012 = 4055.084

Rounding it off to 4 significant figures, it becomes

4.0070 x 1012 = 4055

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%