Review of 1st Semester Topics needed for 2nd Semester Name______p__

Significant Figures (sig figs) Rules

  • All non-zero numbers are significant. 3.14285, 3.143, 4693
  • Zeros between significant digits are significant. 7.0534, 70534, 3023
  • Leading zeros are not significant. 0.7893, 0.0011
  • Trailing zeros are significant if a decimal is present. 360.3,3602, 360.04, 0.03603
  • Use scientific notation to avoid ambiguity. Show sig figs as coefficient. 3600(2sf)3.6x1032

1)Significant figures:Underline and state how many significant figures:

a)10000__

b)10000.__

c)0.0009__

d)0.0900__

e)0.0910__

f)0.9010__

g)901__

h)901.0__

2)Rounding Rules: When rounding, look at the number after the number you are rounding to.

  • If # after # rounding to is <5 round down. Rounding to 2 sig figs: 333330; 0.3330.33;
  • If # after # rounding to is ≥5 round up. Rounding to 3 sig figs: 33353340; 3.3353.34

a)Round to 1 sig figs: 1025______; 1.025______; 0.103______; 10.3______

b)Round to 2 sig figs: 1025_____; 1.025_____; 0.103_____; 103_____; 0.02938_____

c)Round to 3 sig figs: 90342______; 9035______; 0.1256______; 2998______

3)Rounding atomic masses on the periodic table

Round the following elements’masses to the hundredths place, 2 places after the decimal.

ie)oxygen15.99916.00;sodium22.98922.99;beryllium9.0129.01;chromium51.99652.00

a)Nitrogen14.006_____

b)carbon12.010_____

c)hydrogen1.007_____

d)chlorine35.452_____

e)helium4.003_____

f)boron10.811_____

4)Sig figs (Adding and subtracting):Round answer to least precise place in given numbers.

ie) 5.4m-2.13m=3.27m3.3m; 100g+1g=101g100g

Show unrounded answer (1 place more than where rounding), then rounded answer to correct # ofsig figs.

a)1.1+5.437+9.95=______=_____

b)4.78+3.218+5.82=______=_____

c)9.99-6.6=______=_____

d)100-11=______=_____

5)Sig figs (Multiplying and dividing): Round answer to least significant digits in given numbers.

ie) 2.4(15.8)=37.9238;16.8/5.8=2.8962.9; 102.4/51.2=22.00

Show unrounded answer (1 place more than where rounding), then rounded answer to correct # of sig figs.

a)6.2x 13.0=______=_____

b)15.00/3.00=______=_____

c)38,736/478=______=_____

d)55x100=______=_____

6)Multi-step. Show intermediate step, and unrounded answer. Round final answer to correct # of sig figs.

ie) (2.35g+15.6g)/0.03591mL=17.95g/0.03591mL=499.86...g/mL500.g/mL

a)(32.68/14.1 )+73.44=______=______=______

b)(57.28-3.941)x(0.68647)= ______=______=______

c)(3.5x21.3)-71.5=______=______=______

d)23.91/(43.6+14.15)= ______=______=______

e)(35.65-117.8)8.494=______=______=______

7)Scientific notation:Write so only 1 nonzero digit is left of decimal; eliminates place holding zeroes.

  • exponent is negative if decimal is moved right.ie) 0.00111.1x10-3
  • exponent is positive if decimal is moved left.ie) 11001.1x103

a)0.0765______

b)6190.0______

c)90000______

d)0.0090______

e)912.0______

f)837100______

8)Standard notation:

  • if negative exponent, move decimal left. ie) 1.1x10-30.0011
  • if positive exponent, move decimal right. ie) 1.1x1031100

a)2.22x10-3______

b)3.334x104______

c)4.444x10-4______

9)Calculations with Scientific Notation.Show unrounded answer, then rounded answer

  • Adding and subtracting:Must have the same exponent.ie)(2x103)+(10x1021x103)=3x103

a)3.1x104+4.87x105=______=______

b)9.87x104-6.2x103=______=______

  • Multiplying:Multiply coefficients. Add exponents. ie) (3x103)(3x103)=9x106

a)(2.0x103)(3x102)= ______

b)(4.0x101)(5.5x108)= ______

  • Dividing:Divide coefficients. Subtract exponents. ie) (8x106)/(4x103)=2x103

a)8.2x108/4.1x103=______

b)3.63x10-2/1.21x10-6=______

  • Using a calculator:x10xis typed in most calculators as 2ND(top left), EE (key over 7), then whatever x is. Actually typing x 10 or using carrots will give incorrect answers. Know your calculator.

ie) 58/6.022x1023=9.63x10-239.6x10-23

a)9.87x104·6.2x103= ______

b)2.3x102·6.022x1023=______

c)4.359x106/1.19x104=______

10)Conversions: Use conversion factors to convert from 1 unit to another. Put the unit you are given in the denominator. Top unit is what you’re trying to find. Show unrounded answer, then rounded answer.

ie) Convert 9.29x103µmkm. 9.29x103µm x1 m x 1 km =9.29x10-6km

1x106µm 1000m

1000m=1km / 100m=1hm / 1 in=2.54 cm / 1 mi=5280 ft / 12in=1ft / 1 hr=60min / 1day=24hr
1m=100cm / 1m=10dm / 1m=1x106µm / 1lb=453.6g / 1min=60sec / 365days=1yr

a)Convert 16.5yrs______=5.20x108sec

b)Convert100.0 m =6.214x10-2miles

c)Convert 3.2561 dg =7.1784x10-4 pounds(lb)

d)Covert 25 µm ______=4.2x10-25hm

11)Naming Compounds:

  • 1stelement metal? 1st name, ∆ 2ndelement’s end to ide (except polyatomic ions)
  • 1stelement metal not in G1,2,13? 1st name w RN for charge, ∆ 2ndend to ide (except P.A. ions)
  • 1stelementnonmetal? prefixes(≠mono on 1st), ∆ 2nd end to ide
  • 1stelement H w/O?polyatomic ionw/ (ateic acid,iteous acid)
  • 1stelement H w/o O?hydro-ic acid

a)MgCl2______

b)TiSO3 ______

c)Al(OH)3______

d)Fe2O3______

e)NaClO3 ______

f)Pb(CO3)2______

g)N2O4 ______

h)PI5______

i)H2O______

j)H2SO4 ______

k)HBr______

l)H2SO3______

m)HCl ______

n)HNO3 ______

o)HCN ______

12)Formula writing:

  • 1stelement is a metal? Symbols/charges (RN=charge of cation/metal), flip charges, simplify
  • 1stelement is a nonmetal? Symbol w/ prefixes as subscripts, don’t simplify
  • Acid w/hydro? 1st H+, 2ndelement w/charge, flip charges
  • Acid w/o hydro? 1st H+, polyatomic ion w/charge(icate, ousite),flip charges

a)Francium chloride ______

b)cobalt(II)phosphate______

c)magnesium nitrite ______

d)gold(III)chloride______

e)strontium carbonate ______

f)copper(II) sulfate ______

g)diphosphorus pentoxide____

h)nitrogen trioxide______

i)sulfur hexafluoride ______

j)hydrosulfuric acid ______

k)hydrofluoric acid ______

l)hydroiodic acid ______

m)phosphorous acid ______

n)phosphoric acid______

o)carbonic acid ______