When a 3.22 g sample of an unknown hydrate of sodium sulfate, na2so4 . x h2o (s), is heated, h2o (molar mass 18 g) is driven off. the mass of the anhydrous na2so4 (s) (molar mass 142 g) that remains is 1.42g. the value of x in the hydrate is

Explanation:

This is like an empirical formula question, except that you are finding the molar ratio of compounds instead of atoms.

Step 1. Gather the information in one place.

M_r:                                            142             18

           Na₂SO₄·xH₂O(s) ⟶ Na₂SO₄(s) + xH₂O(g)

m/g:              3.22                      1.42

Step 2. Calculate the mass of the water

Mass of H₂O = mass of Na₂SO₄·xH₂O – mass of Na₂SO₄

= 3.22 – 1.42 = 1.80 g

Step 3. Calculate the moles of each product

Na₂SO₄:

     H₂O:

Step 4. Calculate the molar ratios

, so the formula of the compound is Na₂SO₄·10H₂O

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explanation:

the density of gold = 19.3 g/cm3

the relation between density and mass and volume is

density = mass / volume

given :

mass of gold = 13 g

density = 13g / volume = 19.3

volume = 13 /19.3 = 0.67 cm^3

thus volume of gold nugget = 0.67 cm^3