Suppose a laboratory has a 38 g sample of polonium-210. the half-life of polonium-210 is about 138 days.

a. how many half-lives of polonium-210 occur in 1104 days?

b. how much polonium is in the sample 1104 days later?

What atomic or hybrid orbitals make up the sigma bond between br and f in bromine trifluoride, brf3?

50.0 g of copper was dropped into 250.0mL of H2O at 25.0°C in a coffee cup calorimeter. The copper and H2O reached thermal equilibrium at 27.5°C. Calculate the initial temperature of the copper. Specific heat of water is 4.

Solve for C using the equation c=a/b when a=4.7 and b = 1.3

How much heat was absorbed or lost by the surroundings? use 4.184 j/goc for the specific heat of the solution. put your answer in units of kj and make sure the sign is correct?

An element has 6 valence electrons available for bonding which group of the periodic table does the element most likely belong to? group 2 group 4 group 16 group18

What is the ratio of Fe+3 ions to O2 - ions in a neutral compound? a. 1:2 b. 2:1 c. 2:3 d. 3:2

What is the specific heat capacity of a 17.5g sample of an unknown metal that releases 6700J of heat when it cools from 90 to 25 degrees C?

How can equilibrium of a closed system chemical reaction be disturbed? Select all that apply. Adding or removing products or reactants. Keeping the concentration of products and reactants the same. Keeping the temperature of the system constant.

Why does an exothermic reaction need activation energy?

The temperature of 15 grams of water increases by 3.0 degress. how much heat was absorbed by water?