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]
3 years ago
5

One question please help!

Chemistry
1 answer:
Agata [3.3K]3 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
Oh hi thanks for checking in I’m still a piece of garbage ^_^^_^^_^^_^^_^^_^^_^^_^^_^^_^^_^^_^^_^^_^^ - ^
Ad libitum [116K]

Answer:

True

and same lol

7 0
3 years ago
Read 2 more answers
A rigid tank contains 2.4 kg of helium at determine the volume
ddd [48]
The volume is 1.3 for
4 0
3 years ago
(02.01 MC)
inna [77]

It is likely the neutral atom has 6 protons and 6 electrons; while the negatively charged atom has 7 or more electrons.

The mass of an atom, commonly known as the atomic mass is determined by the number of protons and neutrons as electrons have a very low mass.

This means two atoms can have the same number of protons and neutrons, but a different number of electrons, which would make the atom be charged negatively or positively.

Based on this, if there are two atoms, each with 6 protons but one of these is negatively charged it is because the second atom has 1 or more extra.

Neutral atom:

  • This atom has 6 protons and an unknown number of neutrons located in the nucleus.
  • This atom has 6 electrons that orbit the nucleus.
  • The first energetic level will include 2 electrons while the second energetic level will include the 4 remaining electrons.

Negatively-charged atom:

  • This atom has 6 protons and an unknown number of neutrons located in the nucleus.
  • This atom has 7 or even more electrons that orbit the nucleus.
  • The first energetic level will include 2 electrons while the second energetic level will include up to 8 electrons.

Learn more about atoms in: brainly.com/question/13981855

8 0
2 years ago
Scientists follow specific processes in order to determine valid explanations and conclusions from scientific data. Students gra
Rashid [163]
D is the answer. You cannot say that anyone is good at anything because it doesn't say that. And they were surveying the class of 2010
8 0
3 years ago
Read 2 more answers
Sulfur hexachloride is an ionic compound. True False
Gwar [14]
False. This is a covalent bond. You can tell because it uses the prefix “hexa-“ you don’t use prefixes when it’s an ionic compound.
8 0
3 years ago
Read 2 more answers
Other questions:
  • For the reaction 2NOCl(g) &lt;-----&gt; 2NO(g) + Cl2(g), Kc = 8.0 at a certain temperature. What concentration of NOCl must be p
    13·1 answer
  • Wait so wats the answer to this question
    9·1 answer
  • : Citric acid, H3C6H5O7, is a triprotic acid. Consider a buffer system comprising H2C6H5O7 - and HC6H5O7 2- ions. What is the ne
    14·2 answers
  • Which equation is used to help form the combined gas law?
    5·2 answers
  • What is the moden periodic law​
    8·1 answer
  • The rate at which a reaction is proceeding at a specific point in time is called the:______
    12·2 answers
  • the bonds in a molecule of oxygen are blank blank bonds, while the bonds in a molecule of water are blank blank bonds
    7·1 answer
  • This stadium can hold 100,000, or 1 x 10^5, people. The number of atoms in a grain of iron is about 1 x 10^18. Would you need 1 
    14·1 answer
  • Who wanna be friends like frfr
    6·2 answers
  • What biological molecules transport other substances, provide structural
    14·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!