Page 319 - Theory and Problems of BEGINNING CHEMISTRY

308 SCIENTIFIC CALCULATIONS [APP.

A.29. Write the sequence of keystrokes required to do each of the following calculations on your calculator:
(a)3 × 4 2 (b) (3 × 4) 2 (c) −3 2 (d)3 3 (e)3 4
(a) 3 × 4 x 2 = (d) 3 x 2 × 3 =
(b) 3 × 4 = x 2 (e) 3 x 2 x 2

(c) 3 x 2 +/−

A.30. Report the result for each of the following expressions in scientific notation:
6
5
(a) (2 × 10 )(3 × 10 ) −2.0 × 10 7
8 × 10 3 (e) 5.0 × 10 −2
(b) −5
2 × 10 4 ( f ) 2.0 × 10
5.5 × 10 −2 −8.0 × 10 −2
(c) 6 3
2.2 × 10 2 (1.0 × 10 )(8.0 × 10 )
7
−3
(d) (3.5 × 10 )(4.0 × 10 ) (g) 2.0 × 10 8
Ans. (a)6 × 10 11 (d)1.4 × 10 5 (g)4.0 × 10 1
(b)4 × 10 −1 (e) −4.0 × 10 8
(c) 2.5 × 10 −4 ( f ) −2.5 × 10 −4

A.31. Which part of Problem A.27 has a different answer if the precedence rules for calculators are used?
Ans. Part d is different. On the calculator, the quotient a/b is multiplied by c, so the expression (a/b)c is the same
as the value without the parentheses.

A.32. Solve each of the following equations for x.
(a) log x = 1.69 (b) log (x/2.00) = 1.69 (c) log (2.00/x) =1.69

Ans. (a) 49 (b) 98 (c) 0.041

A.33. Report the result for each of the following expressions to the proper number of significant digits:
(a) (103 − 152)/76.1 ( f ) −2.22 + (−3.33) × 12.6
(b) (97 + 17)/15.0 (g) −13.6 × (−22.2)/66.6
3
(c) 222/19.32 − 44.6 (h)2.00 × 3.00 2
(d) (−13) 3 (i) 13.9/(−104 + 20.2)
(e) (−3.59)(77.2)(66.3) (j) 12.4/3.09 − 6.06
Ans. (a) −0.64 (d) −2.2 × 10 3 (g)4.53 (j) −2.05
(b)7.6 (e) −1.84 × 10 4 (h) 72.0
(c) −33.1 ( f ) −44.2 (i) −0.17

A.34. Report the result for each of the following expressions to the proper number of significant digits:
0
1
(a)12.8 − 6.02 (d) (1.28 × 10 ) − (6.02 × 10 )
11
(b)12.8 × 6.02 (e) (1.28 × 10 ) − (6.02 × 10 )
10
(c) −12.8 ÷ 6.02
Ans. (a) 6.8 (b) 77.1 (c) −2.13 (d) 6.8 (e)6.8 × 10 10