Labware and Math Review

choose the best graduated cylinder to make each measurement Choose the best graduated cylinder to make each measurement in a single use. 36 mL of water_____________________ 5.75 mL of a sucrose solution___________________________ 18.5 mL of a NaCl solution ___________________

- 50ml graduated cylinder with markings every 10mL - A 10 mL graduated cylinder with markings every 0.1 mL - A 25mL graduated cylinder with markings every 1mL

Suppose that two students perform a titration experiment multiple times, resulting in the average concentrations reported here. Student A 0.125 ± 0.008 M Student B0.12 ± 0.03 M The more precise work was done by _________________Student B because _________________

- Student A - the students data has a smaller standard deviation

Suppose you are given the mass of each element in a compound sample. To calculate the empirical formula, start by ______________ using__________________________. Then, ___________________________ by ________________________.

- converting the mass of each element to moles - using each elements molar mass - calculate the ratio between the elements - dividing the moles of each element by the smallest number of moles present

When inputting a formula into Excel or other spreadsheet software, what components are required for the formula to function properly? (2 things)

-Closing parentheses for any opening parentheses -An equal sign at the beginning of the formula

When performing an addition or subtraction calculation, significant figures in the calculated result are dictated by the __________________ of the measured numbers . The calculated result should have ____________________________ the measured number in the calculation with the fewest ________________________________.

-decimal places -the same number of digits past the decimal point as - digits past the decimal point

When performing a multiplication or division calculation, significant figures in the calculated result are dictated by the ___________________________ of the measured numbers. The calculated result should have _______________ the measured number in the calculation with the fewest _________________ past the decimal point zero digits.

-significant figures - same number of significant figures as - significant figures

How many liters is 92.7 mL?

0.0927 Liters

What purposes can funnels serve in the lab? (3 purposes)

1- Help for transferring solid chemicals from weigh boats 2- Assistance for pouring liquids into burets 3- Support for filter paper during a gravity filtration

Identify tools that are ideal for cleaning glassware (2 things)

1- detergent and water 2- brushes

Determine where each type of cleaning solution should be discarded after use. Water used to rinse detergent out of a flask: ? Acid solution used to clean a crucible: ? Solvent used to rinse chemicals out of a beaker: ?

1- sink 2- waste container 3- waste container

Perform the calculation, rounding your answer to the proper number of significant figures. 2.74 - 0.00072 =

2.74

Knowing that one day is 24 hours, how many days is 67.0 hours? Type answer:

2.8 days (67 / 24)

Perform the calculation, rounding your answer to the proper number of significant figures. 0.384 + 5.28 + 15.0007 =

20.66

Knowing that one day is 24 hours and one hour is 60 minutes, how many minutes are in 1.9 days?

2736 minutes

Perform the calculation, rounding your answer to the proper number of significant figures. 0.841 x 7.34 x 5.1 =

31.

What is the correct reading for the graduated cylinder in the close-up? Make sure to report your reading with the appropriate significant figures.

40.5 mL (graduated cylinder gives the 40 digit so we estimate one digit beyond to 40.5)

Suppose you are measuring the mass of a solid sample on a balance using a weigh boat. You record the data in a table. Mass of weigh boat 2.762 g Mass of weigh boat and sample 8.802 g What is the mass of the solid sample (in g)?

6.040g

To convert between units, you need to know the relationship between units. For example, one mile equals 5280 feet. This relationship can now be used as a conversion factor, set up as required by the question. For each conversion, choose the correct arrangement of the conversion factor and complete the calculation. 1. Convert 7860 feet to miles 7860 feet×( A )/( B ) A: ? B: ?

A: 1 mile B: 5280 feet

What are the best practices while sharing a lab balance with other students? ( 2 things)

Brush off any chemical dust around the balance after each use. Alert your TA or instructor about any issues with the balance.

one mile equals 5280 feet 0.565 miles×( C )/( D ) C: ? D: ?

C: 5280 feet D: 1 mile

When using a properly stabilized balance, how should you ensure that you get the most accurate mass reading possible? (2 things)

Close the side shields on the balance during reading. Measure the mass of the sample at room temperature.

Which procedure cannot be performed on a hot plate, requiring a Bunsen burner instead?

Heating a crucible to remove water from a hydrate

What should you do every time you are about to heat glassware on a hot plate? ( 3 things)

Inspect the hot plate for frayed cords Check that there are no cracks in the glassware Ensure that the glassware is designed for heating

While setting up a beaker to boil a solution on a hot plate, you notice that the stirring is erratic and unstable. What should you do to stabilize the stirring solution?

Move the beaker to the center of the hot plate. Turn down the stirring speed.

Identify correctly formatted scientific notation.

NUMBER GREATER THAN ONE EXPONET MUST BE 10 TO THE POWER OF SOMETHING

Suppose you heat a 4.31 g sample of a Na2CO3 hydrate. After thorough heating, the mass of the compound is 3.22 g. Based on the data, what is the formula for the hydrate you started with?

Na2CO3 ⋅ 2H2O

What is the average mass, in grams, of the product based on the six trials?

add up all the masses and divide by 6. make sure to include correct sig figs

When is the best time to clean glassware during the lab session?

as soon as practical after use

What should you do if you are using a balance that has persistent fluctuations in mass?

contact your TA or instructor to adjust the balance

To isolate a single variable when rearranging equations, move all other variables to the ________________________ the equation by using __________________ on them and remembering to perform that operation ______________________________. Make sure the rearrangement has the target variable ___________________________ .

other side, the opposite function, on both sides of the equation In the NUMERATOR, not the denominator

Consider the given plot of absorbance vs. concentration. Which line is the best-fit line to represent the black data points?

red

When heating a solution to boiling on a hot plate, start by ___________________________. Then, turn the heat to _______________ to start. If necessary, ____________________, after waiting about ten minutes without seeing boiling.

starting and stabilizing the stir function a medium heat setting turn up the heat setting

To measure out a volume of liquid, start by choosing the appropriate graduated cylinder and moving the bumper to the ______________ of the graduated cylinder to protect it from breakage. Then, pour the liquid into the graduated cylinder until the ______________of the meniscus aligns with the desired volume marking when you look at the graduated cylinder from __________________.

top, bottom, eye level