Answer:
A. because the wood is stored chemical energy and it is converting into heat energy
6= Only the digits 1 and 6 are the actual measured values. Therefore we have only 2 significant figures.
0.3= Zeros used as placeholders are not significant. Zeros that come before non-zero integers are never significant. Example 5: The zeros in 098, 0.3, and 0.000000000389 are not significant because they are all in front of non-zero integers. c. If the zeros come after non-zero integers and are followed by a decimal point, the zeros are significant.
First, divide the given mass of lead (ii) chloride by the molar mass of the compound. The molar mass is equal to 278.1 g/mol.
n = m/M
where n is the number of moles, m is the given mass, and M is the molar mass. Substituting the known values,
n = 473.7 g / 278.1 g/mol
n = 1.7 mols
Then, it is to be remember that as per Avogadro, every mol of a substance contains 6.022 x 10^23 formula units.
N = (1.7 mols)(6.022 x 10^23 formula units/mol)
N = 1.02 x 10^24 formula units
Answer: 1.02 x 10^24 formula units
Answer is: -601,2 kJ/mol
Chemical reaction: Mg(OH)₂ → MgO + H₂O.
ΔHrxn = 37,5 kJ/mol.
ΔHf(Mg(OH)₂) = <span>−924,5 kJ/mol.
</span>ΔHf(H₂O) = <span>−285,8 kJ/mol.
</span>ΔHrxn -enthalpy of reaction.
ΔHf - enthalpy of formation.
<span>ΔHrxn=∑productsΔHf−∑reactantsΔHf.
</span>ΔHf(MgO) = -924,5 kJ/mol - (-285,8 kJ/mol) + 37,5 kj/mol.
ΔHf(MgO) = -601,2 kJ/mol.