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3 years ago

Why is the energy supplied by the cooker greater than that calculated ?

Chemistry

1 answer:

TEA [102]3 years ago

7 0

Answer:

Explanation:

Q1.

(a) 46 200

accept 46 000

allow 1 mark for correct substitution

ie 0.5 × 4200 × 22 provided no subsequent step

(b) Energy is used to heat the kettle.

[3]

Q2.

(a) (approximate same size particles as each other and as liquid and gas) touching

do not accept particles that overlap

regular arrangement (filling the square)

(b) condensing

(d) physical

(e) particles have more kinetic energy

particles move faster

(f) mass of the liquid

specific latent heat of evaporation

(g) 2 × 4 200 × 801

672 000 (J)

an answer of 672 000 (J) scores 2 marks

[11]

Q3.

(a) x-axis labelled and suitable scale

Page 12 of 13

points plotted correctly

allow 5 correctly plotted for 2 marks, 3−4

correctly plotted for 1 mark

allow ± ½ square

line of best fit

(b)

allow ecf from line of best fit in part (a)

0.075 (°C/s)

an answer of 0.075 (°C/s) scores 2 marks

a calculation using an incorrect temperature

scores max 3 marks

ΔE = 1.50 × 900 × 11.5

ΔE = 15 525 (J)

ΔE = 15.525 (kJ)

an answer of 15.525 (kJ) or 15.53 (kJ) or 15.5

(kJ) scores 4 marks

an answer of 15 525 (kJ) scores 3 marks

[10]

Q4.

(a) 80 °C

ΔE = 0.5 × 3400 × 80

ΔE = 136 000 (J)

an answer of 136 000 (J) scores 3 marks

(b) energy is dissipated into the surroundings

allow any correct description of wasted energy

allow any sensible practical suggestion

eg add salt to the water

Page 13 of 13

(d) efficiency = 300/500

efficiency = 0.6

an answer of 0.6 or 60% scores 2 marks

allow efficiency = 60%

an answer of 0.6 with a unit scores 1 mark

an answer of 60 without a unit scores 1 mark

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How do you write chemical formulas

sasho [114]

There are things called "Reactants" and "Products" All chemical equations look something like "A + B →C (+ D...)," in which each letter variable is an element or a molecule (a collection of atoms held together by chemical bonds). The arrow represents the reaction or change taking place. Some equations may have a double-headed arrow (↔), which indicates that the reaction can proceed either forward or backward. When a compound has been written out, you must identify the elements and know their chemical symbols. The first element written is “first name” of the compound. Use the periodic table to find the chemical symbol for the element. So here is an example: Dinitrogen hexafluoride. The first element is nitrogen and the chemical symbol for nitrogen is N. To know the numbers of atoms that are present for each element you can just look at the prefix from the element For example: Dinitrogen has a the prefix “di-“ which means 2; therefore, there are 2 atoms of nitrogen present.

Write dinitrogen as N2.

Now for the second element or "last name" of the compound whatever will follow the first element so like; Dinitrogen hexafluoride. The second element is fluorine. Simply replace the “ide” ending with the actual element name. The chemical symbol for fluorine is F.

But the more you practice with, the easier it will be to decipher chemical formulas in the future and learn the language of chemistry.

Sulfur dioxide: SO2

Carbon tetrabromide: CBr4

Diphosphorus pentoxide: P2O5 ← That is one of the examples I'll give you.

have a gooooood daaaaayy

4 0

3 years ago

The decomposition of N2O to N2 and O2 is a first-order reaction. At 730°C, the rate constant of the reaction is 1.94 × 10-4 min-

grin007 [14]

Answer:

Total pressure 5.875 atm

Explanation:

The equation for above decomposition is

$2N_2O \rightarrow 2N_2 + O_2$

rate constant $k = 1.94\times 10^{-4} min^{-1}$

Half life $t_{1/2} = \frac{0.693}{k} = 3572 min$

Initial pressure $N_2 O = 4.70 atm$

Pressure after 3572 min = P

According to first order kinematics

$k = \frac{1}{t} ln\frac{4.70}{P}$

$1.94\times 10^{-4} = \frac{1}{3572} \frac{4.70}{P}$

solving for P we get

P = 2.35 atm

$2N_2O \rightarrow 2N_2 + O_2$

initial 4.70 0 0

change -2x +2x +x

final 4.70 -2x 2x x

pressure of $O_2$ after first half life = 2.35 = 4.70 - 2x

x = 1.175

pressure of $N_2$ after first half life = 2x = 2(1.175) = 2.35 ATM

Total pressure = 2.35 + 2.35 + 1.175

= 5.875 atm

5 0

3 years ago

Read 2 more answers

Why is a cis-1,3-disubstituted cyclohexane more stable thanits<br> trans isomer?

anzhelika [568]

Answer:

Explanation has been given below

Explanation:

In diaxial conformation of cis-1,3-disubstituted cyclohexane, 4 gauche-butane interactions along with syn-diaxial interaction are present. Hence it readily gets converted to diequitorial conformation where no such gauche-butane interaction is present
In two possible conformations of trans-1,3-disubstituted cyclohexane, 2 gauche-butane interactions are present in each of them.
Hence cis-1,3-disubstituted cyclohexane exists almost exclusively in diequitorial form. But trans-1,3-disubstituted cyclohexane has no such option.

Trans-1,3-disubstituted cyclohexane experiences gauche butane interaction in each of the two conformations.
Therefore cis-1,3-disubstituted cyclohexane is more stable than trans conformation

5 0

3 years ago

Which element has properties most similar to those of chromium

Vedmedyk [2.9K]

Chromium is a chemical element with symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard and brittle metal which takes a high polish, resists tarnishing, and has a high melting point.

7 0

4 years ago

Name the separation technique illustrated in the picture<br>

o-na [289]

The picture isn’t included

3 0

3 years ago