How many moles of copper are needed to react with sulfur to produce 0.25 moles of copper(I) sulfide according to the following reaction:
2 Cu + S à Cu2S

0.5 mole

Explanation:

The equation for the reaction is given below:

2Cu + S —> Cu2S

We can calculate the mole of copper (Cu) needed to react with sulphur (S) to produce 0.25 mole of copper(I) sulfide (Cu2S) by doing the following:

From the balanced equation above,

2 moles of Cu reacted to produced 1 mole of Cu2S.

Therefore, Xmol of Cu will react to produce 0.25 mole of Cu2S i.e

Xmol of Cu = 2 x 0.25 = 0.5 mole

Therefore, 0.5 mole of copper (Cu) will react with sulphur (S) to produce 0.25 mole of copper(i)sulfide (Cu2S)

- 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