Honors Chem Molar Masses/Percent Composition/Hydrates/Empirical Formula

Just like a few hard questions

What is all considered to be a mole in chemistry?

1. 12.00 grams of ¹²C

2. 6.022×10²³ atoms of ¹²C

3. an amount

If you have 10.0L of a 1.5 M solution of NaOH, how many moles NaOH is it?

1.5 mol/1L * 10.0L/1 = 15

How many moles is 2.02 grams of H₂?

2 hydrogens = 2.02g/1 × 1mol/2.02g = 1

Find the Empirical Formula for 1.0995g Na, 0.6700g N, and 1.5304g O.

Na: 1.0995g/1 × 1mol/22.99 = 0.0478 N: 0.6700g/1 × 1mol/14.01 = 0.0478 O: 1.5304/1 × 1mol/16 =0.09565 Take smallest number and divide by each. Na ~1 N~1 O~2 = NaNO₂

What should you do if you gett 1.4,1.5, or 1.6 in the Empirical formula?

Multiply each postulate by 2

What Empirical formula would you get for octance?

ocatne: C₈H₁₈ must reduce to lowest form = C₄H₉

How many moles of water are found in each mole of hydrated chromium III chloride?

if…

9.65g before heat

5.73g after heat

9.65-5.73= 3.92g of water

H₂O: 3.92g/1 1mol/18.02g = 0.217

CrCl₃: 5.73g/1 × 1mol/158.35g =0.0362

divide water by crystal/smallest number H₂O = 6

What is the percent composition of oxygen in a substance that is 5.2g before reacting with oxygen and 7.4g after?

7.4g-5.2g = 2.2g of oxygen

2.2/7.4 = 29.7%