(0.04)c(33.7-23.5)+(0.08)c(33.7-39.6) Find C

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Homework Help Overview

The problem involves determining the specific heat capacity of saltwater using a heat transfer equation. The scenario describes two samples of saltwater at different initial temperatures being mixed, and the final temperature is provided. The original poster notes that they conducted a mini-lab to measure the temperatures and masses of the samples.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the use of the heat transfer equation Q=mcΔT and the concept of heat lost and gained. There is a focus on the challenge of finding the specific heat capacity when both substances are the same (saltwater) and the implications of not having a known reference heat capacity.

Discussion Status

The discussion highlights the difficulty of solving the problem without a known reference for the specific heat capacity. Some participants confirm that the approach is not viable under the given conditions, while others suggest checking the consistency of the provided temperatures.

Contextual Notes

Participants mention the context of a classroom setting where the teacher may present misleading scenarios to test students' understanding. There is an acknowledgment of the limitations imposed by the problem setup, particularly the lack of a reference heat capacity for saltwater.

Andrei316
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Sorry if the title is against the rules or anything, I just wanted to be specific as possible :P
1. Homework Statement
V1(Saltwater) = 40g = 0.04kg
V2(Hot-Saltwater) = 80g = 0.08kg
Ti(Saltwater) = 23.5oc
Ti(Hot-Saltwater) = 39.6oc
Tf = 33.7c

Question: A cup of 40g saltwater is at 23.5c & A cup of 80g saltwater is at 39.6c, Find the specific heat capacity of salt water. **I measured these myself because it was a mini-lab so the specific heat capacity might not be exactly 3.99x103J.

2. Homework Equations
I asked my grade 11 physics teacher and this could be solved by using QLOST + QGAINED and Q=mcΔT. I asked my friends and they couldn't figure it out too ;-;

The Attempt at a Solution


I tried using everything and did anything I could do ...but I still couldn't get the answer of 3.99x103J. I can easily figure it out if I was it was 2 different substances and at least one heat capacity, but finding only c because they are both salt water confuses me.
m1cΔT1 + m1cΔT1
(0.04)c(33.7-23.5)+(0.08)c(33.7-39.6)
 
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Without a reference (known input heat or something with a known heat capactiance), the whole approach cannot work. You are comparing salt water with salt water.
 
mfb said:
Without a reference (known input heat or something with a known heat capactiance), the whole approach cannot work. You are comparing salt water with salt water.
Oh alright, yeah I just wanted to make sure it wasn't possible. My teacher does this thing when he tricks us to check if we actually do our work... it's really annoying but he does teach us why it's impossible and stuff like that. Thanks for your help and time :)
 
You can check the numbers for consistency: Check if the mixing temperature is right.
 

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