A scientist performed an experiment to learn how the thickness of a piece of wood affects its ability to support weight without breaking. The scientist prepared three different pieces of wood and applied weight until they broke. The results are shown in the table below. Thickness of Wood Breaking Weight 1 cm 15 kg 2 cm 29 kg 3 cm 42 kg Which variable is intentionally controlled by the experimenter? A. The type of scale used to measure the weight O B. The thickness of the wood O C. The breaking weight D. The number of pieces of wood

answer: - first one is the correct answer. .

explanations: - potassium sulfide is and cobalt(ii) chloride is .

charge on k is +1, charge on s is -2, charge on co is +2 and charge on cl is -1.

in a double replacement reaction the ion exchange takes place. in general the reaction looks like:

if one of the product is insoluble as per solubility rules then a precipitate of it is formed.

when we mix the aqueous solutions of potassium sulfide and cobalt(ii) chloride then chloride ion goes with potassium ion and sulfide ion goes with cobalt ion and the balanced equation is written as:

k and cl has equal charges, similarly co and s has equal charges and hence no subscripts are used for the product side.

as per the solubility rules, cos is insoluble and so it's precipitate is formed.

looking at the given choices, first choice is correct.