It's Peggy Sue's birthday and she's about to blow out the candles on her cake. Brother Roger stops the party when he shouts: "Look at that! Chemical and physical changes taking places on your birthday cake!"How would you respond to Roger?
A) Roger is incorrect. The melting wax is a physical change but there is no chemical change taking place.
B) Roger is correct. Lighting the match is a chemical change and burning the candles is a physical change.
C) Roger is correct. The melting wax is a physical change and the burning candle wick is a chemical change.
D) Roger is incorrect. Only a chemical change is taking place as evidenced by the light and heat of the burning candles.
Answers
Melting of wax is a physical change and chemical change is the burning of candle.
What is chemical and physical changes?
Chemical changes are those changes by which composition of the original matter changes and physical changes are those changes by which only appearance of the matter changes.
In the given activity:
- Melting of wax is a physical change because during this composition of wax not changes but only outer structure changes.
- Burning of candle and lighting the match are chemical change as it produces energy in the form of heat and light.
Hence, Roger is correct ie. The melting wax is a physical change and the burning candle wick is a chemical change.
To know more about physical and chemical changes, visit the below link:
brainly.com/question/17166994
#SPJ2
Related Questions
What is the pressure of 64 grams of O2 in a 1L container at a temperature of 10°C?
During glycolysis, for every 6 moles of glucose that enter the pathway, how many moles of atp are used? how many moles atp are generated? how many moles of nadh are used? how many moles of pyruvate are made?
How many moles of sodium hydroxide are produced when 1.00 mol sodium peroxide reacts with water
If the reaction is at dynamic equilibrium at 500 K, which statement applies to the given chemical system?The forward and reverse reactions no longer occur. The rates of the forward and reverse reactions are unequal. The concentrations of the products and reactants do not change. The forward reaction stops at 500 K.
Answers
Answer:
The answer is
2.0 g/mL
Explanation:
The density of a substance can be found by using the formula
From the question
mass = 10 g
volume = 5 mL
The density of the substance is
We have the final answer as
2.0 g/mL
Hope this helps you
Answers
A. What is the limiting reagent?
B. How many grams of the excess reactant remains?
C. How many grams of each product is formed?
D. If 12 grams of NaNO3 actually formed in the reaction, what is the percent yield of this reaction?
Answers
Answer:
Explanation:
Pb(NO3)2 (aq) + 2 NaI (aq) --> PbI2 (s) + 2 NaNO3 (aq)
MM for each compound -
Pb(NO3): 207 + 14x2 + 16x3x2 = 331
PI2: 207 + 127x2 = 461
NaI: 23 + 127 = 150
NaNO3: 23 + 14 + 16x3 = 85
Moles of Pb(NO3)2 = 50/331 = 0.15
Moles of NaI = 30/150 = 0.2
Ratio of moles is 1:2
So NaI is limiting
Limited to 0.2/2 = 0.1 mole of Pb(NO3)2
Excess = 0.15 - 0.1 = 0.05 mole
Mass remains = 0.05x331 = 16.55 grams
Moles of NaNO3 formed = Moles of NaI reacted = 0.2
Mass = 0.2x85 = 17 grams
Moles of PbI2 formed = Moles of Pb(NO3)2 reacted = 0.1
Mass = 0.1x461 = 46.1 grams
If 12 grams of NaNO3 actually formed in the reaction,
percent yield = 12/17x100% = 70.6%
Answer:
Explanation:
Moles of Pb(NO3)2 = mass/molecular mass
= 50.0 grams/(207.20*1 + 14.01*2 + 16*6)
= 50.0 grams/331.22
= 0.15 moles
Moles of NaI
= 30/(22.99+126.9)
= 30/149.89
= 0.2 Moles
A. NaI is less 2x Pb(NO3)2 so NaI is the limiting reagent.
B. The ratio is 1 to 2 so there is 0.15 - 0.2/2 = 0.05 mole
or 16.78 grams of Pb(NO3)2 left.
C. As NaI is limiting, only 0.2 Moles of NaNO3 is formed.
Mass = Moles * Molecular Mass
Molecular Mass of NaNO3 can be calculated as:
Na - 22.99
N - 14.01
O - 3(16) = 48
23+14+48 = 85gram / mole
Thus, Mass = 0.2*85 = 17 gram of NaNO3
Mass is conserved in a chemical reaction.
Mass of PbI2 can be calculated as:
50+30-16.78-17
= 46.3 gram of PbI2
Mass =
12.75
Thus, 12.75g of Sodium Nitrate can be formed
Answers
Answers
Answers
Answer:
the change in internal energy per mole of sucrose is 5989 KJ/mol
Explanation:
Since the calorimeter is a bomb calorimeter , where the volume remains constant
ΔE= Qrx
And assuming no heat losses to the surroundings
Qv + Qrx = 0
Cc*ΔT - Qrx = 0 ,
Qrx = Cc * ΔT = 7.50 KJ/°C * 22 °C = 165 KJ
the change in internal energy is calculated dividing by the number of sucrose moles involved n. the molecular weight of sucrose is
Mw= 12* 12g/mol + 22* 1g/mol + 11* 16 g/mol = 342 g/mol
n = m / Mw = 10 g / 342 g/mol = 0.029 mol
the change in internal energy per mole of sucrose is
Δe= ΔE/n = 165 KJ/0.029 mol = 5989 KJ/mol