Heat and Energy Transfer Help

In summary, the individual masses of silver and gold were 0.013 kg and 0.007 kg respectively, with a total mass of 0.02 kg.
  • #1
horcruxes
1
0

Homework Statement


Twenty grams of silver and gold (total mass of the gold plus the silver is 20 grams) is used to convert 1 g of ice at -3°C to steam at 100°C. If both the silver and the gold are at their melting points at the beginning and the final temperature of the silver, gold and steam is 100°C, what was the individual mass of the silver and the gold?

Homework Equations


Q1=Q2
Q=mCpΔT
Q=mLvap
Q=mLfus

The Attempt at a Solution


mAu= x kg
mAg= (.02-x) kg
mice= .001 kg
ΔTAu= 1064-100 = 964
ΔTAg= 962-100 = 862
CpAu = 130 J/kg[itex]\cdot[/itex]C°
CpAg = 230 J/kg[itex]\cdot[/itex]C°mAuCpAuΔTAu + mAgCpAgΔTAg = miceCpiceΔTice + miceLfus + mwaterCpwaterΔTwater + mwaterLvap
x(130)(964) + (0.02-x)(230)(862) = (0.001)(2100)(3) + (0.001)(333) + (0.001)(4186)(100) + (0.001)(2260)
125320x + 3965.2 - 198260x = 6.3 + 0.333 + 418.6 + 2.26
-72940x = -1980.5
x = 0.027 kg

My answer is over 0.02 kg (20g) and because I'm solving for the mass of gold, it was to be less than 20 grams. I've done this problem about four times already and I know I'm doing something wrong, I just can't figure out what.
Any help is greatly appreciated, thank you!
 
Physics news on Phys.org
  • #2
Look at the largest term on the right, it dominates,

(0.001)(4186)(100) = 418

and make the left side as small as possible,

x(130)(964) + (0.02-x)(230)(862) --> .02*130*964 = 2500

The problem as stated is wrong or your values are wrong?
 
  • #3
@Spinnor --thank you! I figured out what was wrong --both my values for heat of fusion and heat of vaporization were wrong --I had to multiply them each by 103 to get the right answer, whoops! Thanks for the help though!
 

1. What is the difference between heat and energy transfer?

Heat is a form of energy that is transferred from one object to another due to a difference in temperature. Energy transfer, on the other hand, is the movement of energy from one place to another, including the transfer of heat.

2. How is heat transferred?

Heat can be transferred through three main methods: conduction, convection, and radiation. Conduction is the transfer of heat through direct contact between two objects. Convection is the transfer of heat through the movement of fluids or gases. Radiation is the transfer of heat through electromagnetic waves.

3. What factors affect the rate of heat transfer?

The rate of heat transfer is affected by several factors, including the temperature difference between the objects, the thermal conductivity of the materials involved, the surface area of the objects, and the distance between them.

4. How does insulation affect heat transfer?

Insulation helps to reduce the rate of heat transfer by providing a barrier between two objects with different temperatures. This prevents heat from escaping or entering the insulated space, keeping the temperature constant.

5. What are some real-life examples of heat and energy transfer?

Some common examples of heat and energy transfer include heating a pot of water on a stove, the movement of warm air from a heater, the transfer of heat from the sun to the Earth's surface, and the cooling of a hot cup of coffee through convection and evaporation.

Similar threads

  • Introductory Physics Homework Help
Replies
2
Views
3K
  • Introductory Physics Homework Help
Replies
1
Views
13K
  • Introductory Physics Homework Help
Replies
1
Views
1K
  • Introductory Physics Homework Help
Replies
3
Views
7K
  • Introductory Physics Homework Help
Replies
21
Views
3K
  • Introductory Physics Homework Help
Replies
8
Views
2K
  • Introductory Physics Homework Help
Replies
18
Views
5K
  • Introductory Physics Homework Help
Replies
4
Views
20K
  • Introductory Physics Homework Help
Replies
1
Views
1K
  • Introductory Physics Homework Help
Replies
8
Views
4K
Back
Top