Please answer all of the questions! thank you!! Question 4 (3 points) Five penni

Question

Please answer all of the questions! thank you!!

Question 4 (3 points) Five pennies are placed in a graduated cylinder containing 10mL of water. The volume of material in the graduated cylinder measures 15.1mL after the pennies are added. lfthe mass of the pennies is 5.74g, what is the density of the pennies? Round your answer to 2 decimal places. Question 5 (4 points) A student experimentally determineds the specific heat of zinc to be 0.98 JVgoC, 0.75 J/goC, 0.45J/goC, 0.87 J/goC, and 0.25 J/goC, in 5 separate trials. The actual specific heat of zinc is 0.39 J/goC. Based on this information, discuss the accuracy and precision of the student's data. Question 6 (3 points) When zinc metal is added to 6M hydrochloric acid, bubbles are observed and the test tube feels warmer. Based on this information, has a chemical reaction occurred? Be sure to cite evidence based on the information provided that supports your condusion. Save Question 7 (3 points) Explain how an emission spectra occurs. Be sure to discuss the states of the electron and what specifically occurs that causes this phenomenon. Question 8 (3 points) A student places 20% sucrose solution in a dialysis bag. This bag is designed to function as a semipermeable membrane to allow water to pass through, but not the sucrose. This bag is then suspended in a container of distilled water for 2 hours. At the end of 2 hours, the student carefully dries and measures the mass of the dialysis bag and sucrose solution. Based on this experimental setup, explain in general what you would expect the student to observe at the end of their experiment regarding the mass of their dialysis bag. Why do you expect these results?

Explanation / Answer

1.

Mass of the pennies = 5.74 gms, mass of single pennie= 5/5.74=0.87gm

Volume of water =10ml, volme of water+pennies =15.1ml, Volume of pennies= 15.1-10=5.1ml

Density of the penny = 0.87/5.1 g/ml=0.171 g/ml

2. Accuracy is defined as the tendency of an instrument to match the actual value while precision is defined as the ability of measurement to be reproduced consistently. Based on the experiments conducted and the results, the data is having bad accuracy and bad precision.

3.

The following reaction occurs when Zinc is dissolved in water

Zn +2HCl------à ZnCl2 +H2

The bubbling is do with formation of hydrogen gas

4. When external energy is supplied to an atom , the energy is absorbed by the electrons and reach an excited state. As the atom absorbs energy, it is in excited state and tries to regain the original position by emitting energy in the form of radiation and this is known as emission

5. Osmosis is the passage of water from a dilute solution through a semi-permeable membrane to a more concentrated solution, The semipermeable bas is permeable to water, not sucrose. Water flows from the bag into the container containing distillled water and the mass of the bag gets reduced.

6.

. The reaction is Cu+1/2O2----->CuO

The reaction suggests one moles of Copper reacts with 0.5 moles of oxygen to give 1 mole of CuO.

Molar ratio of Cu :O2= 1 0.5

Atomic weight of Copper = 63.5 gms and molecular weight of oxygen =32

Moles of copper = 63.5/63.5= 1, moles of oxygen= 32/32= 1

Actual ratio = 1:1

So Excess reactant is oxygen and limiting reactants is Copper. Hence , 1 mole of CuO is formed. Mass of CuO= 63.5+16= 79.5 gms

7. Limiting reactant

8.

Baking soda is NaHCO3 and Acetic acid is CH3COOH. The reaction is

NaHCO3 + CH3COOH------>CH3COONa +H2O

1 mole of Baking soda reacts with 1 mole of CH3COOH completely

Molecular weights : NaHCO3= 84, CH3COOH= 60

Moles : NaHCO3= 1/84= 0.0119 moles, Beaker 1 : acetic acid = molarity* Volume (l)= 1*50/1000= 0.05, beaker 2:   0.75*50/1000 =0.0375moles, third beaker = 1.5*50/1000 = 0.075 moles

No beaker reacts completely since all the cases, there is excess of acetic acid.

9.

10. permieter, density and mass

11.The hypothesis is that placebo is not responsible for baldness and if at all any curing of baldness is there that is due to the medicine only.

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