Answer: A) grinding coffee beans
Explanation:
A physical change is defined as a change in which there is alteration in shape, size etc. No new substance gets formed in these reactions.
A chemical change is defined as a change in which a change in chemical composition takes place. A new substance is formed in these reactions.
1. Grinding coffee : Only change in size takes place, thus a physical change
2. Baking a cake: the chemical reaction occurs by combination of flour with oxygen , thus a chemical change.
3.:converting water to hydrogen and oxygen: The decomposition iof water takes place, thus is a chemical change
4.Burning of coal: the chemical reaction occurs by combination of carbon with oxygen , thus a chemical change.
This<span> will require'' </span>266.9kJ''<span> of heat energy
</span>
To calculate the energy required to raise the temperature of any given substance, here's what you require:
The mass of the material, <span>m</span>
Answer:
t = 7.58 * 10¹⁹ seconds
Explanation:
First order rate constant is given as,
k = (2.303
/t) log [A₀]
/[Aₙ]
where [A₀] is the initial concentraion of the reactant; [Aₙ] is the concentration of the reactant at time, <em>t</em>
[A₀] = 615 calories;
[Aₙ] = 615 - 480 = 135 calories
k = 2.00 * 10⁻²⁰ sec⁻¹
substituting the values in the equation of the rate constant;
2.00 * 10⁻²⁰ sec⁻¹ = (2.303/t) log (615/135)
(2.00 * 10⁻²⁰ sec⁻¹) / log (615/135) = (2.303/t)
t = 2.303 / 3.037 * 10⁻²⁰
t = 7.58 * 10¹⁹ seconds
Answer:
0.00757 grams
Explanation:
Find the molar mass of the compound: which is 60.05.
The molar mass is basically just the sum of all the atomic masses of each of the elements.
Then multiply the molar mass by the number of moles in the compound, which is 1.26 x 10^-4 moles.
Your answer should be 0.00757 grams.
he required empirical formula based on the data provided is Na2CO3.H2O.
<h3>What is empirical formula?</h3>
The term empirical formula refers to the formula of a compound which shows the ratio of each specie present.
We have the following;
Mass of sodium = 37.07-g
Mass of carbonate = 48.39 g
Mass of water = 14.54-g
Number of moles of sodium = 37.07-g/23 g/mol = 2 moles
Number of moles of carbonate = 48.39 g/61 g/mol = 1 mole
Number of moles of water = 14.54/18 g/mol = 1 mole
The mole ratio is 2 : 1: 1
Hence, the required empirical formula is Na2CO3.H2O
Learn more about empirical formula : brainly.com/question/11588623
