Consider the equations below. (1) ca(s) + co2(g) + 1 2 o2(g) → caco3(s) (2) 2ca(s)+o2(g) → 2cao(s) how should you manipulate these equations so that they produce the equation below when added? check all that apply. cao(s) + co2(g) → caco3(s) reverse the direction of equation (2) multiply equation (1) by 3 multiply equation (2) by 1/2

Answer : The correct options are, reverse the direction of equation (2) and multiply equation (2) by 1/2.

Explanation :

According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.

According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation.

The main given balanced chemical reaction is,

Now we have to determine the main chemical reaction from the given two intermediate reactions.

(1)

(2)

Now reverse the equation (2), multiply equation (2) by 1/2 and then add both the equations, we get the main chemical reaction.

(1)

(2)

Now add both the equations, we get:

Hence, the steps used for the main reaction are, reverse the direction of equation (2) and multiply equation (2) by 1/2.

frequency, z, and the collision density, z, in carbon dioxide (co2), r 180 pm at 30 °c and 120 kpa

the density of gold = 19.3 g/cm3

the relation between density and mass and volume is

density = mass / volume

given :

mass of gold = 13 g

density = 13g / volume = 19.3

volume = 13 /19.3 = 0.67 cm^3

thus volume of gold nugget = 0.67 cm^3