Answer:
Atoms is the answer
Explanation:
Based on protons, neutrons and electrons
A definition of "matter" more fine-scale than the atoms and molecules definition is: matter is made up of what atoms and molecules are made of, meaning anything made of positively charged protons, neutral neutrons, and negatively charged electrons.
Answer:
constant appearance
Explanation:
this mean that a pure substance will have a constant appearance ,colour,density ,melting point and boiling point
The chemical equation is missbalaced.
The right balanced chemical equation is:
<span>2NaHCO3(s) + 129 kJ ---> Na2CO3(s) + H2O(g) + CO2(g)
Then, now you know that 2 moles of NaHCO3 requires 129 kJ heat, and you just need to convert 25.5 grams of NaHCO3 into number of moles to calculare the amount of heat needed.
A) Number of moles in 25.5 g of NaHCO3, n:
n = grams / molar mass
molar mass NaHCO3 = 23 g/mol + 1g/mol + 12g/mol + 3*16g/mol = 84 g/mol
n = 25.5 g / 84 g/mol = 0.304 mol
B) Heat required
Make the proportion with the theoretical ratio:
2mol / 129 kJ = 0.304 mol / x
=> x = 0.304 mol * 129 kJ / 2 mol = 19.608 kJ
Answer: 19.6 kJ
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