Question 28 How many calories are required to raise the temperature of 205 g of water from 35.0°C to 80.0°C?
(specific heat of water- 1 cal/g °C)

Asample of radium-226 will decay 1/4 of its original amount after 3200years. what is the half-life of radium-226?

__can be defined as which velocity changes

Modern pennies are composed of zinc coated with copper. a student determines the mass of a penny to be 2.482 g and then makes several scratches in the copper coaling (to expose the underlying zinc). the student puts the scratched penny in hydrochloric acid, where the following reaction occurs between the zinc and the hcl (the copper remains undissolved): zn(s) + 2 hcl(aq) → h2(g) + zncl(aq)the student collects the hydrogen produced over water at 25 °c. the collected gas occupies a volume of 0.899 l at a total pressure of 79 j mmhg. calculate the percent zinc (by mass) in the penny. (assume that all the zn in the penny dissolves.)