27 Answered Questions for the topic Lab

04/30/20

#### Finding the Ksp value of Ca(OH)2

A student determined the solubility of Ca(OH)2 in 0.200 M CaCl2 as 0.0026 mol/L. Calculate the Ksp value for Ca(OH)2 using these data. I found this to be =7.03E-8, but it says that I have entered... more

02/28/20

#### Finding the Average Epsilon and Molarity of Unknown Solution

Stock Solution: 8.8×10-5 MSolution #1: 1.809×10-5 MSolution #2: 1.046×10-5 MYou measure the absorbance of each solution (at λmax = 524 nm) and obtain the following results: ... more

10/03/18

#### Hydrogen Emission Spectrum Lab

So I've recently did a hydrogen emission spectrum lab.   These were the four wavelengths I got:   Red         675 nm Green      570 nm Blue        460 nm Purple      425 nm   These are the... more

08/27/18

#### How to make a buffer?

So I have to make a 0.02 M Sodium Phosphate buffer @ pH of 7, easy enough I use monosodium and disodium phosphate as the acid and base, I used the henderson hasselbach equation. But now I have to... more

04/23/18

#### What grows on an alkaline peptone broth apart from Vibrio?

I have done an experiment where growth on an alkaline peptone was monitored and then we innoculated a TCBS media, however no growth occured on the TCBS media so i was wondering what else could... more

02/15/18

#### Williamson Ether Synthesis LAB QUESTION!?

Why use acetonitrile instead of toulene in a Williamson Ether Synthesis? (Phenol, NaH, 1-bromopropane)?Also, why use aqueous Na2CO3 instead of distilled water when extracting?
Lab

12/19/17

#### Empirical formula of the oxide of tin

Hhgghjbb bnbgccccc bbjb. Hbggh bbhfxc ddssyh huh. Hhggcvvbbbbvvvvv b high. Hhgghhbb bhhhhhhb

11/30/17

#### We can prepare oxygen gas by decomposing hydrogen peroxide. There are many other chemical reactions that generate gases as one of their products.

Lets consider the reaction between zinc metal and hydrochloric acid as such an example. Write a procedure that explains how you would collect the gas produced from this reaction in the laboratory.
Lab

11/29/17

#### The combustion of ethane produces carbon dioxide and water.

The combustion of ethane produces carbon dioxide and water. If 27.6 g C2H6 are burned in the presence of excess ait (O2) and 76.7 g of carbon dioxide are produced, what is the percent yield?
Lab

11/29/17

#### In a lab experiment, 17.5 g of iron II bromide react with 14.2 g of potassium sulfide.

In a lab experiment, 17.5 g of iron II bromide react with 14.2 g of potassium sulfide. Upon completion, 4.3 g of iron II sulfide were obtained. Determine the limiting reactant, theoretical yield... more

11/01/17

#### Refractive Index - ORGANIC CHEMISTRY LAB

A student attempts to separate a sample of cyclohexane and ethylbenzene by distillation. After the distillation the student obtains an n 20D of 1.4355 for what should be pure cyclohexane with a... more

10/31/17

#### Tea contains about 3% caffeine by mass. Assuming each tea bag contained 2.25 g of tea, did you recover the expected amount of caffeine from two tea bags?

So what is the expected amount of caffeine? Is it 0.0675g or is it 0.135g?  In lab, I recovered 0.018g of caffeine

10/21/17

#### CALCULATING PARTITION COEFFICIENT - Organic Chemistry Lab

1. Calculate the partition coefficient of caffeine in water/methylene chloride from the following data: 10.3 g/100 mL for methylene chloride and 2.04 g/100 mL for water.   MY ANSWER:    K =... more

09/29/17

#### Rf values TLC - Organic Chemistry LAB

For my developing solvent, I used 6:4 hexane:ethyl acetate. For my reference spot, I mixed some salicylic acid and ethyl acetate. And for my test spot, I used some impure aspirin and ethyl... more
Lab

03/30/17

Chemistry
Lab

03/14/17

#### trying to get concentration

Use the dilution equation to calculate the molar concentration of sodium bsiulfite and potassium iodate after mixing for each th solutions.after mixing hso and after mixing io3

03/16/16

#### Chemistry Problem:stoichiometry

Al+S8 -->Al2S3-How many moles of aluminum are required to produce 56.9 grams of sulfur?-5.0 grams of aluminum sulfide is needed. How many grams of sulfur is required to make it?

03/11/16

#### Stoichiometry Lab

CuCO3.Cu(OH)2--> CO2+H2O+2CuO How many grams of Copper II oxide are produced if you start with 1.01 g of Copper II carbonate.

03/10/16

#### stoichiometry problem

HCl + Na2SO4 → NaCl + H2SO4-If you start with 20.0 grams of hydrochloric acid, how many grams of sulfuric acid will be produced assuming there is 0% error?-How many moles of sulfuric acid should be... more

03/10/16

#### stoichiometry problem

Mg + NaF → MgF2 + Na-If you start with 5.5 grams of sodium fluoride, how many grams of magnesium fluoride will be produced if there is no error?-Determine how many formula units of sodium fluoride... more

11/11/15

#### how do you make a 10ml solution with a .40m concentration

I know it has to do with molars and making a solution that we can measure how much light goes through it because we are doing concentration.

10/26/15

#### Biology Lab - Absorbance vs. Light Intensity

Hello,   I recently performed a photosynthesis experiment regarding change in absorbance over time vs. intensity of light. 4 tubes of solutions containing chloroplasts, .1M PO4 buffer, water, and... more

10/20/15

#### Is citric acid plus baking soda an endothermic reaction?

Please explain if it is endothermic or exothermic?

09/11/14

#### Hypothesis sounds okay or not

THIS COLOR OF FLOWERS EFFECT THE AMONT OF POLLINATORS, COLOR DOES HAVE EFFECT ON THE NUMBER OF POLLINATORS. IF COLOR HAS AN EFFECT ON THE NUMBER OF POLLINATORS THEN ORANGE FLOWERS WOULD HAVE MORE... more

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