Posted by Rachel | Posted in Coffee and Accessories | Posted on 13-06-2009
Tags: beaker coffee, beaker coffee cups, beaker coffee maker, beaker coffee mug, beaker coffee youtube, coffee, mug, science, shopping, wishlist
Chemistry problems I am having trouble with. Calorimetry?
Here are the problems. Can someone please guide me through the steps of solving them? I don’t necessarily need the answer although it would be nice! :p
A chemistry student must mix a beaker of hot water with a beaker of cold water in order to obtain a temperature of 37.0°C (body temperature). The temperature of the cold tap water is 22.0°C, and the temperature of the hot tap water is 65.3°C. If a student starts with 60.8 g of cold water, what mass of hot water must be added to reach 37.0°C?
In a coffee-cup calorimeter, 1.82 g of NH4NO3 is mixed with 73.7 g of water at an initial temperature of 25.00°C. After dissolution of the salt, the final temperature of the calorimeter contents is 23.21°C. Assuming the solution has a heat capacity of 4.18 J/°C·g and assuming no heat loss to the calorimeter, calculate the enthalpy change for the dissolution of NH4NO3 in units of kJ/mol.
heat lost + heat gained =0
Q = m x specific heat x delta T
60.8 x 4.18 ( 37.0 – 22.0 ) + mass x 4.18 ( 37.0 – 65.3 )=0
3812.16 + mass x ( – 118.294)=0
mass = 32.2 g
hope helps
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