1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
andrew-mc [135]
2 years ago
5

One question please help!

Chemistry
1 answer:
Agata [3.3K]2 years ago
3 0
<span>1 trial : you have nothing to compare the result with - you don't know if it's a mistake.
2 trials : you can compare results - if very different, one may have gone wrong, but which one?
3 trials : if 2 results are close and 3rd far away, 3rd probably unreliable and can be rejected.

******************************

First calculate the enthalpy of fusion. M, C and m,c = mass and specific heat of calorimeter and water; n, L = mass and heat of fusion of ice; T = temperature fall.

L = (mc+MC)T/n.

c=4.18 J/gK. I assume calorimeter was copper, so C=0.385 J/gK.

1. M = 409g, m = 45g. T = 22c, n = 14g
L = (45*4.18+409*0.385)*22/14 = 543.0 J/g.

2. M = 409g, m = 49g, T = 20c, n = 13g
L = (49*4.18+409*0.385)*20/13 = 557.4 J/g.

3. M = 409g, m = 54g, T = 20c, n = 14g
L = (54*4.18+409*0.385)*20/14 = 547.4 J/g.

(i) Estimate error in L from spread of 3 results.
Average L = 549.3 J/g.
average of squared differences (variance) = (6.236^2+8.095^2+1.859^2)/3 = 35.96
standard deviation = 5.9964
standard error = SD/(N-1) = 5.9964/2 = 3 J/g approx.

% error = 3/547 x 100% = 0.5%.

(ii) Estimate error in L from accuracy of measurements:
error in masses = +/-0.5g
error in T = +/-0.5c

For Trial 3
M = 409g, error = 0.5g
m = 463-409, error = sqrt(0.5^2+0.5^2) = 0.5*sqrt(2)
n =(516-463)-(448-409)=14, error = 0.5*sqrt(4) = 1.0g
K = (mc+MC)=383, error = sqrt[2*(0.5*4.18)^2+(0.5*0.385)^2] = 2.962

L = K*T/n
% errors are
K: 3/383 x 100% = 0.77
T: 0.5/20 x 100% = 2.5
n: 1.0/14 x 100% = 7.14

% errors in K and T are << error in n, so we can ignore them.
% error in L = same as in n = 7% x 547.4 = 40 (always round final error to 1 sig fig).

*************************************

The result is (i) L= 549 +/- 3 J/g or (ii) L = 550 +/- 40 J/g.
Both are very far above accepted figure of 334 J/g, so there is at least one systematic error in the experiment or the calculations.
eg calorimeter may not be copper, so C is not 0.385 J/gK. (If it was polystyrene, which absorbs/ transmits little heat, the effective value of C would be very low, reducing L.)
Using +/- 40 is probably best (more cautious).
However, the spread in the actual results is much smaller; try to explain this discrepancy - eg
* measurements were "fiddled" to get better results; other Trials were made but only best 3 were chosen.
* measurements were more accurate than I assumed (eg masses to nearest 0.1g but rounded to 1g when written down).

Other sources of error:
L=(mc+MC)T/n is too high, so n (ice melted) may be too small, or T (temp fall) too high - why?
* it is suspicious that all final temperatures were 0c - was this actually measured or just guessed? a higher final temp would reduce L.
* we have assumed initial and final temperature of ice was 0c, it may actually have been colder, so less ice would melt - this could explain small values of n
* some water might have been left in container when unmelted ice was weighed (eg clinging to ice) - again this could explain small n;
* poor insulation - heat gained from surroundings, melting more ice, increasing n - but this would reduce measured L below 334 J/g not increase it.
* calorimeter still cold from last trial when next one started, not given time to reach same temperature as water - this would reduce n.
Hope This Helps :)
</span>
You might be interested in
HELP PLEASE! There is a water-filled continental rift in Iceland. What type of plate boundary would cause this rift? *
ad-work [718]
1.A- convergent
2.A- lower mantle

Good Luck!!
7 0
2 years ago
Read 2 more answers
What 2 chemicals react together during photosynthesis
Nitella [24]

Answer:

The photosynthesis chemical equation states that the reactants (carbon dioxide, water and sunlight), yield two products, glucose and oxygen gas. The single chemical equation represents the overall process of photosynthesis.

Explanation:

Definition: the process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a byproduct.

Hope this helps!

Can I get brainliest?

5 0
3 years ago
What coefficient for O2 demonstrates the law of conservation of mass?
olga2289 [7]

Answer:

2

Explanation:

The coefficient for O is 2 and this is an example of a combustion reaction. With the help of the coefficient 2 infront of oxygen, this equation now demonstrates law of conservation of mass.

6 0
3 years ago
What is a geochemist
Nimfa-mama [501]
An expert in or student of the branch of science concerning the chemical composition of the earth and its rocks and minerals.
3 0
2 years ago
A student sets up the following equation to convert a measurement.
Sholpan [36]

Answer:

–0.13 Pa.m²

Explanation:

From the question given above, the following data were obtained:

Measurement (Pa.mm²) = –1.3×10⁵ Pa.mm²

Measurement (Pa.m²) =?

We can convert from Pa.mm² to Pa.m² by doing the following:

1 Pa.mm² = 1×10¯⁶ Pa.m²

Therefore,

–1.3×10⁵ Pa.mm² = –1.3×10⁵ Pa.mm² × 1×10¯⁶ Pa.m² / 1 Pa.mm²

–1.3×10⁵ Pa.mm² = –0.13 Pa.m²

Thus, –1.3×10⁵ Pa.mm² is equivalent to –0.13 Pa.m².

6 0
3 years ago
Other questions:
  • The balanced equation for combustion in an acetylene torch is shown below: 2C2H2 + 5O2 → 4CO2 + 2H2O The acetylene tank contains
    7·2 answers
  • In a neuron relaying a message to its neighbor, where do nerve impulses in a neuron travel to last?
    12·1 answer
  • How many grams of chlorine gas are in a 17.8 liter sample at 1.1 atmospheres and 29 degrees Celsius
    7·1 answer
  • if you begin with 210.3 g of Cl2, how many grams of HCl will you end up with? CH4 + 3Cl2 → CHCl3 + 3HCl *
    11·1 answer
  • A student prepares 150. mL of a 2.00 M Ba(OH)2 aqueous solution in lab. What mass of Ba(OH)2 is fully dissolved in the solution?
    11·1 answer
  • What is the pH of a substance that has a hydrogen ion concentration of 8.8
    11·1 answer
  • HELP ME ASAP PLEASEEEE
    11·1 answer
  • What are “condensation nuclei”?
    14·1 answer
  • Rosa drew a flow chart of the carbon cycle.
    9·2 answers
  • How many protons would the element with the atomic number 10 contain
    15·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!