Unit 4 Practice Test Chapter 7 Concepts (Mole Concept) (Percent Composition) (Empirical Formulas)
1. Convert g Cu(NO 3 ) 2 to moles of copper (II) nitrate g Cu(NO 3 ) 2 = mol Cu(NO 3 ) 2 g Cu(NO 3 ) 2 1 mol Cu(NO 3 ) 2 X 1 mole = molar mass (Use the Periodic Table)
53.75 g Cu(NO 3 ) 2 = mol Cu(NO 3 ) 2 g Cu(NO 3 ) 2 1 mol Cu(NO 3 ) 2 X g = g Cu(NO 3 ) g x g x g g g x Cu O N On calculator: ÷ =
2. How many molecules of carbon tetrachloride are in 2.58 moles of CCl 4 ? 2.58 mol CCl 4 = molecules CCl 4 1 mol CCl 4 molecules CCl 4 X 1 mole = 6.02 x molecules 6.02 x x On calculator: 2.58 x 6.02 E 23 = E 10 24
3. What volume (in Liters) of ammonia gas is in 2.57 moles of NH 3 at STP? 2.57 mol NH 3 = L NH 3 1 mol NH 3 L NH 3 X 1 mole = 22.4 L for On calculator: 2.55 x 22.4 =
%CX 100 = 80.0 g 44.0 g = 55 % C 4.A sample of a compound containing carbon and hydrogen has a mass of 80.0 g. Experimental procedures show that 44.0 g is carbon, and the remaining 36.0 g is hydrogen. What is the percentage of Carbon in this sample?
g CuCl 2 CuCl g35.45 g x g g = x 1 %ClX 100 = g g = % Cl 5. What is the percentage of chlorine in CuCl 2 ? 29 Cu Cl 35.45
6.0 g C= g C 1 mol C x 0.50 mol C 16.0 g O= g O 1 mol O x 0.50 mol = 1 = 2 CO 2 6 C Find the empirical formula of a gas that contains 6.0 g carbon and 16.0 g of oxygen. Name the gas. 8 O Carbon dioxide Name: ___________________ Empirical Formula: ______________