This question is based in mole ratios. for every mole of cl2, 2 moles of NaCl will be produced. so half of the moles of NaCl gives the moles of Cl2 required. therefore divide 0.35 by 2
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The temperature change is 23 °C.
<em>q = mC</em>Δ<em>T</em>
Δ<em>T</em> = <em>q</em>/(<em>mC</em>)
<em>m</em> = 355 g
∴ Δ<em>T</em> = (34 000 J)/(355 g × 4.184 J·°C⁻¹g⁻¹) = 23 °C
<em>Note</em>: The answer can have only <em>two significant figures</em> because that is all you gave for the amount of heat absorbed.
Hey, for #1, it's 1, 1, 1 because it's already balanced!
For #2, it's 1, 2, 1, 1 since the product side has 2 Cl's but left side only had 1.