Cherylanne mixes together chemical a and chemical b in a test tube, forming chemical c. the mixture instantly turns cool to the touch. she then adds chemical d, and the reaction becomes hot and explodes. what can be known about this situation? chemicals a and b form an endothermic reaction, and chemicals c and d form an exothermic reaction. chemicals a and b form an exothermic reaction, and chemicals c and d form an endothermic reaction. chemicals a and c form an endothermic reaction, and chemicals b and d form an exothermic reaction. chemicals a and b form an exothermic reaction, and chemicals b and d form an endothermic reaction.

Answer : Chemicals A and B form an endothermic reaction, and chemicals C and D form an exothermic reaction.

Explanation :

Endothermic reaction : When the system absorb heat from the surrounding then the surrounding become cool.

Exothermic reaction : when the system releases heat into the surrounding then the surrounding become hot.

According to the question,

when we mixed chemical A and chemical B together in a test tube to form chemical C, the mixture become cool. This means that the system is absorbing heat from the surrounding and thus the reaction is called a endothermic reaction.

And when we added chemical D in chemical C, the new mixture becomes hot and explodes. This means that the system is releasing heat into the surrounding and thus the reaction is called as exothermic reaction.

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms