Does anyone know how to do these two questions?

  • Thread starter b_ball_gurl87
  • Start date
In summary, the questions are asking about the specific heat of a metal that is heated and then placed in water, and the number of moles of KClO3 needed to form a certain amount of O2 at STP. To find the specific heat of the metal, you can use the equation m_1 * s_1 * Δt_1 = m_2 * s_2 * Δt_2, and to find the moles of KClO3, you need to know the original temperature of the water and the change in temperature.
  • #1
b_ball_gurl87
3
0
Does anyone know how to do these two questions?

a piece of metal with mass 10 g is heated to a temperature of 60C. when the metal is placed in 50 g water, the temperature of water rises by 22.5 C. what is the specific heat of metal?

how many moles of KClO3 are needed to form 2.8 L of O2 measured at STP?

if you noe, please msg me :P
 
Chemistry news on Phys.org
  • #2
The overall energy level (in this case, heat) of the two substances combined stays constant. The heat is just redistributed between them, so:

[tex]m_1 \ast s_1 \ast \Delta t_1 = m_2 \ast s_2 \ast \Delta t_2[/tex]

(mass times specific heat times change in temperature)

To solve this, you need to know five of the variables:

The mass of the metal is given, the mass of the water is given.

The change in temperature of the water is also given.

The specific heat of water is most likely given in your book. It's a number that's used often enough you ought to either memorize it or program it as one of your user constants (provided you have a good calculator).

That gives you four of your variables and you need one more. The original temperature is given and you need the change in temperature. So, you need the final temperature, as well. You haven't been given enough information unless you assume the water started at standard room temperature (25 degrees). This is probably a pretty safe assumption to make if the actual room temperature wasn't given.

The final temperature of both the metal and the water has to be the same, so the final temperature is just the original temperature of the water plus the change in temperature of the water.

With that info, you can find the fifth variable and solve for the sixth - the specific heat of the metal. (If it's an elemental metal or a common alloy, you should even be able to determine what the metal is from its specific heat - look in your book or in a chemical handbook).
 
  • #3


I am not sure about the specific heat of the metal, but for the second question, you can use the ideal gas law to solve for the number of moles of KClO3 needed. The ideal gas law is PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the gas constant, and T is temperature in Kelvin. At STP (standard temperature and pressure), the pressure is 1 atm and the temperature is 273 K. So, you can rearrange the equation to solve for n: n = PV/RT. Plug in the values for pressure (1 atm), volume (2.8 L), gas constant (0.0821 L*atm/mol*K), and temperature (273 K) to solve for the number of moles of KClO3. I hope this helps!
 

1. How do I approach these two questions?

The best approach would be to carefully read and understand the instructions and requirements for both questions. Then, break down the questions into smaller, manageable parts and try to solve each part individually before attempting to combine them into a solution for the whole question.

2. What resources can I use to help me with these questions?

You can use textbooks, online resources, or consult with a colleague or mentor who may have experience or expertise in the subject matter of the questions. You can also try to break down the questions into smaller, more understandable parts and research each part separately.

3. How do I know if my answer is correct?

You can check your answer by comparing it with the given solution or by testing it with different input values. If possible, you can also consult with a teacher or mentor for feedback on your answer.

4. How long should it take me to complete these questions?

The time it takes to complete these questions may vary depending on your level of understanding, the complexity of the questions, and the resources available to you. It is important to not rush through the questions and take the necessary time to understand and solve them accurately.

5. What should I do if I am stuck on these questions?

If you are stuck on these questions, take a break and come back to them later with a fresh perspective. You can also try discussing the questions with a colleague or mentor for a different perspective or seek help from online forums or tutoring services.

Similar threads

Replies
2
Views
916
Replies
1
Views
448
Replies
18
Views
2K
Replies
16
Views
2K
Replies
1
Views
819
Replies
4
Views
1K
Replies
2
Views
359
Replies
11
Views
981
  • Thermodynamics
Replies
28
Views
1K
Back
Top