The reaction between 0.0272 g of Mg with an excess of water was carried out in an ice calorimeter. The volume of water decreased by 0.19 mL during the reaction.

a) Write the equation that occurs. Is it a redox?
b) Calculate the enthalpy of reaction?

i have no clue how to approach this questions....soo can someone show me how or give me the steps :) thx

45kj/mol

Sure! Let's break down the steps to solve this question:

a) Write the equation that occurs. Is it a redox?
To write the equation, we need to know that magnesium reacts with water to form magnesium hydroxide and hydrogen gas. The balanced chemical equation for this reaction is:

2 Mg + 2 H2O -> 2 Mg(OH)2 + H2

To determine whether it is a redox reaction, you need to check if there is a change in oxidation states of elements in the reaction. In this case, magnesium starts with an oxidation state of 0 and ends with an oxidation state of +2, so it has been oxidized. Meanwhile, hydrogen starts with an oxidation state of +1 in water and ends with an oxidation state of 0 in hydrogen gas, so it has been reduced. Therefore, this reaction is indeed a redox reaction.

b) Calculate the enthalpy of reaction
To calculate the enthalpy of reaction (ΔH), you can use the equation:

ΔH = q / n

where ΔH is the enthalpy change, q is the heat gained or lost by the reaction, and n is the number of moles of the reactant.

First, calculate the heat gained or lost by the reaction (q) using the equation:

q = mcΔT

where q is the heat gained or lost, m is the mass of the water, c is the specific heat capacity of water, and ΔT is the change in temperature.

In this case, since the reaction is carried out in an ice calorimeter, we can assume the heat gained or lost by the reaction is equal to the heat gained or lost by the water. Therefore, we can use the equation q = mcΔT to calculate q.

Given that the volume of water that decreased during the reaction is 0.19 mL, we can assume that the total volume of water is equal to this. So the mass of the water is equal to 0.19 g (since the density of water is 1 g/mL). The specific heat capacity of water (c) is approximately 4.18 J/g°C.

Now, we need to calculate the change in temperature (ΔT) of the water during the reaction. Unfortunately, this information is not provided in the question. So, if you have this information, replace ΔT with the change in temperature. Otherwise, you won't be able to calculate the enthalpy of reaction (ΔH) without this missing data.

I hope this breakdown helps you understand the steps to approach this question!