click below

click below

Normal Size Small Size show me how

# Chemistry Review SF

### Significant Figures

Question | Answer |
---|---|

What is an example of a number when non-zero digits are always significant? How many significant figures does it have? | 13.2 - three significant figures |

How many significant digits does 7003 have? Why? | 7003 has four significant figures because zeroes between two significant figures are always significant. |

Why would 0.0071 only have two significant digits? | Zeroes in front of all non-zero numbers are not significant, but they act as placeholders |

What is an example of a number when zeros to the right of the decimal place are significant? How many significant figures does it have? | 43.00 - four significant figures |

How many significant digits does 9800 have? | Two significant digits |

Why does 9.800 x 10>3 have four significant figures? (9.800 times 10 to the power of 3) | If zeroes are measured, they are significant by using the scientific notation. |

Why type of value is considered to be infinitely precise? | Counted values (i.e 34 students in a class) are considered to be infinitely precise, so they have an infinite number of SD. (1.e. 34 students can also be considered as 34.00000000 students) |

Why is the four in 4πr^2 considered to be 4.000000? | Coefficients in a formula are infinitely precise, so they have an infinite number of SD's. |

What is a conversion factor? | A conversion factor could be anything like 1kg/1000g or 100cm/m. It is infinitely precise. |

What is 2489.2 x 56.4? | Since 56.4 has three SD's, then our final number must have 3 significant digits. 2489.2 x 56.4 = 140390.88 (140 000 - 3SD...counted zeroes= 1.40×10>5 final answer |

How many SD's does 5002 have? why? | 4SD's because zeroes are in between 2 non-zeroes. |

How many SD's does 50.002 have? why? | 5SD's because zeroes are in between non-zeroes. |

500 | 1SD because zeroes can serve as placeholders |

When would 500 have two or three Significant Figures? Why? | 5.0×102 - 2SD 5.00×102 - 3SD This is because zeroes to the right of the decimal place are significant |

How many significant figures would 500.0 have? Why? | 4SD because zeroes are to the right of a significant figure and a decimal place. |

Round 0.001775 to two Significant figures. | 0.0018 To get this, first determine the number of SD's. Drop all digits after last significant place below 5. However if that digits is above 5, round up the value of the last significant figure. |

Round 8792 to two Significant Figures. | 8800 To get this, first determine the number of SD's. Drop all digits after last significant place below 5. However if that digits is above 5, round up the value of the last significant figure. |

Why would 3.76+14.83+2.1=20.7? | The answer can only have as many decimal places. Since 2.1 has the least amount of decimal places, the final answer must be rounded to 1/10 of a decimal place. 3.76+14.83+2.1=20.67 (only need 1 decimal place...rules of rounding makes 20.67=20.7) |

What is 22.37 x 3.10 x 85.75? Why? | 5950 The final answer may only show as many SD's as the measurement showing the least amount of SD. 22.37 x 3.10 x 85.75 = 5946.50525 (since 3.10 has the least amount of SD's...three...the final answer must be rounded to 3SD's) |

Does 0.0005 have one, four or five SF's? | 0.0005= 5x10>-4 Therefore, only the is significant so there is only 1SF |

What is (3.45x10>7)(6.25x10>5)? Why? | (3.45 x 6.25) (10>7 x 10>5)= 21.5625 x 10>12= 2.16 x 10>13...Final answer (Change to correct sic.not and round to correct number of S.D's) |

Why would (3.5 x 10>8)/(6.6 x 10>9)=5.3 x 10>3? | 1. Divide coefficients and subtract exponents (0.530303 x 10>4) 2. Change to correct sci.not and round to correct S.D (5.3 x 10>3) |

What is (3.76 x 10>4)+(5.5 x 10>2)? why? | 3.8 x 10>4 1. Move decimals to get the same exponents (5.5 x 10>2....0.055 x 10>4...2SF) 2. Add coefficients (3.815 x 10>4) 3. Round = 3.8 x 10>4 |

What is accuracy? | Accuracy of a value is how close the measured or experimental value is to the actual/true.predicted value |

What does % error compare? How is it calculated? | % error compares measured and actual values. %error=((measured value-actual value)/(actual value))∙100 |

What is the experimental error and hos is it calculated? | The experimental error is calculated by subtracting the accepted value (A) form the observed/experimental value (O) exp. error= O-A |

If the measured value of a piece of metal is 52g, but the actual value is 60g, then what is the percent error and the experimental error? | %error= -13% (underestimated measured value by 13%) exp.error= -8g (underestimated exp. value by 8g) |

What is the one value needed to calculate %error? | The actual value |

A man steps on a scale and tells him that he weighs 140lbs, when he actually weighs 155lbs. Find the: a) %error b) experimental error | a) -9.7% error b) -15lbs Therefore the measured value is too low, or too underestimated. |

If a woman is measured to be 165lbs, when she is actually 155lbs, what is the scale's: a)%error b)experimental error | a) 6.4% b)10lbs (The greater the errors the less accurate a measurement is!) |

What is precision? | Precision is the consistency of a result or how reproducible it is. Precision depends on the unit used to measure - the smaller the unit, the more precise the measurement is |

What is the difference between accuracy and precision? | Measurements can be equally precise, but not totally accurate. Two students measure 50cm and 130cm (equally precise, both measurements to nearest cm). If actually 51cm (%error=-1.96%) and 130.5cm (%error= -0.38%)...measures are not equally accurate. |

What would be a more precise way of saying 16 years old? | 16yrs, 4mt, 5days, 13hrs, 7min, 6sec |

Write the number of SD's for: 24.7kg | 3 |

Write the number of SD's for: 247.7ml | 4 |

Write the number of SD's for: 247.701mg | 6 |

Write the number of SD's for: 0.247.01L | 5 |

Write the number of SD's for: 8.930 x 10>5 km | 4 |

Write the number of SD's for: 2.5 g | 2 |

Write the number of SD's for: 0.0003 ml | 1 |

Write the number of SD's for: 923.2 g | 4 |

How many SF would 2400g have if you had measured the quantity? | 4SD This is because... (2.400 x 10>3 = 2400) |

If you have no idea how a value of 1300km was measured, how many SD's would it have? | 2SD This is because zeroes after a non-zero number are insignificant, they only act as placeholders |

Perform the calculation and express the answer in the correct number of sig.figs. 55.671g + 45.78g | 101.45g |

Perform the calculation and express the answer in the correct number of sig.figs. 1.9mm + 0.62mm | 2.5mm |

Perform the calculation and express the answer in the correct number of sig.figs. 87.9478L - 86.25L | 1.70L |

Perform the calculation and express the answer in the correct number of sig.figs. 0.350ml + 1.70ml + 1.019ml | 3.07ml |

Perform the calculation and express the answer in the correct number of sig.figs. 5.841g x 6.03g | 35.2g>2 |

Perform the calculation and express the answer in the correct number of sig.figs. 0.6kg/15L | 0.04kg/L OR 4 x 10>-2 |

Perform the calculation and express the answer in the correct number of sig.figs. 17.51g/2.2cm>3 | 8.0g/cm>3 |

Write the number of sig.figs for: 3.545 | 4 |

Write the number of sig.figs for: 308 | 3 |

Write the number of sig.figs for: 0.000876 | 3 |

Perform the calculation and express the answer in the correct number of sig.figs. 5.672g + 92.21g | 97.88g |

Perform the calculation and express the answer in the correct number of sig.figs. 32.34km x 93.1km | 3010km>2...write as sci.not = 3.01 x 10>3 km>2 |

Perform the calculation and express the answer in the correct number of sig.figs. 66.0ml x 0.031ml | 2.0ml>2 |

Perform the calculation and express the answer in the correct number of sig.figs. 1.12g/92ml | 0.12g/ml |

Perform the calculation and express the answer in the correct number of sig.figs. 1.2m x 3.33m | 4.0m>2 |

Perform the calculation and express the answer in the correct number of sig.figs. 1.0m/0.3m | 3.3m |

Perform the calculation and express the answer in the correct number of sig.figs. 1.0000/0.30000 | 3.3333 |

Perform the calculation and express the answer in the correct number of sig.figs. 1/3.00000000 | 0.3 |

Perform the calculation and express the answer in the correct number of sig.figs. 1.000000000/3 | 0.3 |

What is 3 millionths in scientific notation? | 3 x 10>-6 |

What us a micrometer? | 1mm = 1000micrometers (um) |

Write the answer in meters and in scientific notation. 800 000 000 000 000 000 000 000 km | (8 x 10>26)m |

Write the product in scientific notation 0.04 x 10>9 | 4 x 10>7 |

Perform the calculation: 357.89 - 0.002 | 357.888 rounded to... 357.89 Final Answer |

Perform the calculation: 84.675 - 3 | 81.675 rounded to... 82 Final Answer |

Is 500m/hr a conversion factor? | NO |