If we dissolve 25g KCl in 100g of water, what is the solution concentration?

2. how is heavy water different from normal water

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.)

Ok, so i have 2 questions. try to answer them both: (the topic is fire) 1) how can you represent the chemical reaction of fire? 2) what kind of bond is formed in this chemical reaction