How would I calculate these? I have the answers because there from a previous test.
1) How much heat is required to raise the temperature of a 5.52-g sample of iron ( specific heat = 0.450 J/g C) from 25.0 degrees C to 79.8 degrees C?
2) You mix 60. mL of 1.00 M silver nitrate with 25 mL of 1.63 M sodium chloride. What mass of silver chloride should you form?
1)
a = mass Fe x specific heat Fe x (Tfinal-Tinitial)
2)
This is a limiting reagent problem. I know that because amounts are given for BOTH reactants.
AgNO3 + NaCl ==> AgCl(s) + NaNO3
mols AgNO3 = M x L = ?
mols NaCl = M x L = ?
Using the coefficients in the balanced equation, convert mols AgNO3 to mols AgCl.
Do the same to convert mols NaCl to mols AgCl.
It is likely that these two values will not be the same which means one of them is wrong; the correct answer in limiting reagent problems is ALWAYS the smaller value and the reagent producing that value is the limiting reagent.
Use the smaller value and convert to grams. g AgCl = mols AgCl x molar mass AgCl.
To calculate the heat required in the first question and the mass of silver chloride formed in the second question, you'll need to use specific formulas. I'll explain the steps for each problem so that you understand how to calculate them.
1) Calculating heat required:
The formula for calculating heat is:
Q = m * c * ΔT
Where:
Q = heat energy
m = mass
c = specific heat capacity
ΔT = change in temperature
Given values:
m = 5.52 g
c = 0.450 J/g°C
ΔT = (final temperature - initial temperature) = (79.8°C - 25.0°C)
To solve, substitute the values into the formula:
Q = 5.52 g * 0.450 J/g°C * (79.8°C - 25.0°C)
Calculate the value in the parentheses:
Q = 5.52 g * 0.450 J/g°C * 54.8°C
Multiply all the values together:
Q ≈ 135 J
Therefore, the heat required to raise the temperature of the iron sample is approximately 135 J.
2) Calculating mass of silver chloride formed:
To calculate the mass of silver chloride formed, you need to consider the stoichiometry of the reaction between silver nitrate (AgNO3) and sodium chloride (NaCl). The balanced equation is:
AgNO3 + NaCl → AgCl + NaNO3
From the equation, you can see that one mole of silver nitrate reacts with one mole of sodium chloride to form one mole of silver chloride.
Given values:
Volume of silver nitrate (AgNO3) solution = 60 mL
Volume of sodium chloride (NaCl) solution = 25 mL
Molarity of silver nitrate (AgNO3) solution = 1.00 M
Molarity of sodium chloride (NaCl) solution = 1.63 M
Step 1: Convert the volumes to liters:
Volume of silver nitrate solution (V1) = 60 mL = 0.060 L
Volume of sodium chloride solution (V2) = 25 mL = 0.025 L
Step 2: Calculate the number of moles of each substance:
Number of moles of AgNO3 = Molarity * Volume (in liters) = 1.00 M * 0.060 L
Number of moles of NaCl = Molarity * Volume (in liters) = 1.63 M * 0.025 L
Step 3: Determine the limiting reagent:
The limiting reagent is the one that is completely consumed in the reaction. To find it, compare the number of moles of AgNO3 and NaCl. The one with fewer moles will be the limiting reagent.
Step 4: Convert the limiting reagent to the mass of AgCl:
Based on the balanced equation, the molar ratio between AgNO3 and AgCl is 1:1. Therefore, the number of moles of AgCl formed will be equal to the number of moles of the limiting reagent.
Finally, multiply the number of moles of AgCl by the molar mass of AgCl (143.3 g/mol) to obtain the mass of AgCl formed.
Please note that for a more accurate calculation, you may need to account for the volume change in the final answer due to the formation of AgCl.