1)A piece of metal with a mass of 5.50 grams changed in temperature from 25 to 55 degrees celsius when 21.3 joules was absorbed. What is the specific heat of the metal?
a)0.256
b)0.129
c)3.91
d) 7.75
e)0.710 Jg^-1 C^-1
I chose 7.75 because I did 5.50/21.3 and then multiplied by 30.
2)Which of the following equations represents a reaction for which the delta H can be called a standard enthalpy of formation, delta Hf?
a) FeO(s) + CO2(g) -> FeCO3(s)
b) 1/2 N2(g) + 2 O(g) -> NO2(g)
c) 2 Na(s) + Cl2(g) -> 2 NaCl(s)
d) Ba(s) + N2(g) + 3 O2(g) -> Ba(NO3)2(s)
e) more than one of the four equations above are standard enthalpies of formation.
I chose answer e.
Are these correct?
1.
21.3 = mass x sp.h. x delta T
sp.h. = 21.3/(5.50*30) is not 7.75.
2.
I agree with d.
Ok for number one i got 0.129 and for number 2 did you mean that my answer choice of e was correct or that just equation d is correct? Thank you for your help!!
For the first question, the specific heat of a substance can be determined using the equation:
q = m * c * ΔT
where:
q is the heat absorbed or released by the substance
m is the mass of the substance
c is the specific heat capacity of the substance
ΔT is the change in temperature
In this case, we know the mass of the metal (5.50 grams), the change in temperature (30 degrees Celsius), and the heat absorbed (21.3 joules). We need to rearrange the equation to solve for c:
c = q / (m * ΔT)
c = 21.3 J / (5.50 g * 30 °C)
c ≈ 0.129 J/g°C
So the correct answer for the specific heat of the metal is b) 0.129 J/g°C.
As for the second question, to determine if the reaction can be considered a standard enthalpy of formation (ΔHf) reaction, we need to check if all the reactants are in their standard states and the balanced equation represents the formation of one mole of the product.
Looking at the options:
a) FeO(s) + CO2(g) -> FeCO3(s)
b) 1/2 N2(g) + 2 O(g) -> NO2(g)
c) 2 Na(s) + Cl2(g) -> 2 NaCl(s)
d) Ba(s) + N2(g) + 3 O2(g) -> Ba(NO3)2(s)
None of the given equations represent the formation of one mole of a compound from its constituent elements in their standard states. Therefore, the correct answer is e) more than one of the equations above are standard enthalpies of formation.
So your answer for the second question is incorrect.