Answer: noble gasses
Explanation: zoom on on the red section and look at the key for what red means.
The mass of the solid product of the reaction is determined by weighing.
The answer to this question would be: alkaline earth metal
Alkali earth metal is the second column group of the periodic table. In this group, the element has 2 extra electrons in their outer cells. That is why most of this metal has 2+ charge.
Their neighbor is the alkali metal which was the first column of the periodic table. The name is similar so don't confused and mix them each other.
In order to solve this question, we must apply the conservation of mass. The total number of nucleons (upper number) and protons (lower number) must be equal before and after the decay. The new nucleon number is
218 - 4
= 214
And new proton number is
84 - 2
= 82
Next, we must identify which element has the proton number 82. That would be lead, Pb.
Therefore, the answer is
5. ²¹⁴Pb₈₂
Given:3.40g sample of the steel used to produce 250.0 mLSolution containing Cr2O72−
Assuming all the Cr is contained in the BaCrO4 at the end.
(0.145 g BaCrO4) / (253.3216 g BaCrO4/mol) x (250.0 mL / 10.0 mL) x (1 mol Cr / 1 mol BaCrO4) x (51.99616 g Cr/mol / (3.40 g) = 0.219 = 21.9% Cr
