We also can use dimensional analysis for solving problems.
Significant Figure Review questions…. (answers on the next page)
Question 1
Give the correct number of significant figures for 4500, 4500., 0.0032, 0.04050
Question 2
Give the answer to the correct number of significant figures: 4503 + 34.90 + 550 = ?
Question 3
Give the answer to the correct number of significant figures: 1.367 - 1.34 = ?
Question 4
Give the answer to the correct number of significant figures: (1.3 x 103)(5.724 x 104) = ?
Question 5
Give the answer to the correct number of significant figures: (6305)/(0.010) = ?
Challenge Dimensional Analysis Question…
How many atoms of hydrogen can be found in 45 g of ammonia, NH3?
We will need three unit factors to do this calculation, derived from the following information:
1.
1 mole of NH3 has a mass of 17 grams. (1 mole of NH3 = 17 grams NH3) .
2. 1 mole of NH3 contains 6.02 x 1023 molecules of NH3. (1 mole of NH3 = 6.02 x 1023 molecules of NH3)
3. 1 molecule of NH3 has 3 atoms of hydrogen in it. (1 molecule of NH3 = 3 atoms of hydrogen )
We also can use dimensional analysis for solving problems.
Answers: (1) 2, 4, 2, 4 (2) 5090 (3 significant figures - round to the tens place - set by
550) (3) 0.03 (1 significant figure - round to hundredths place) (4) 7.4 x 107 (2 significant figures
- set by 1.3 x 103) (5) 6.3 x 105 (2 significant figures - set by 0.010)