An aqueous solution that has a hydrogen ion concentration of 1.0 x 10^-8 mole per liter has a pH of

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

TEA [102]

Answer:

Explanation:

Q1.

(a) 46 200

accept 46 000

allow 1 mark for correct substitution

ie 0.5 × 4200 × 22 provided no subsequent step

2

(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

(c) solid

(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

2

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

(c) Δθ = 11.5 (°C)

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

(c) put a lid on the pan

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

7 0

3 years ago

Which statement best describes the reaction pathway graph for an exothermic reaction but not an endothermic reaction? It has a h

ruslelena [56]

Answer: "The reactants are higher in energy than the products"

Explanation:

The exothermic reactions are characterized by the release of heat to the surroundings. The reactants lose heat that is delivered to the surroundings which implies that the products will be lower in energy than the reactants.

The hills that you can see in a reaction energy diagram are not related with the final change of energy. The hills are an indication of the activation energy needed to start the reaction, but they do not measure the change of energy from the products to the reactants.

The enthalpy that is a state variable that identifies the content of heat. Then the change of enthalpy for the exothermic reactions is negative, meaning that the energy of the products is lower than the energy of the reactants.

3 0

4 years ago

Read 2 more answers

In your own words, describe two conditions that are necessary for an eclipse to occur

Rzqust [24]

1. the Moon must be in line with the Earth and Sun - New Moon for a solar eclipse and Full Moon for a lunar eclipse.2. the Moon must be at one of its nodes. Most of the time the Moon at New or Full passes above or below the Sun because its orbit is tilted relative to the ecliptic. An eclipse can occur only when it is at a node, in other words crossing the ecliptic.

4 0

3 years ago

Does acid in your stomach make you unhealthy?

Delvig [45]

No because it burns the food that u had and leaves it more space?????? I

8 0

4 years ago

Read 2 more answers

The carbon atoms in graphite and the carbon atoms in diamond have different

kicyunya [14]

Answer:

<u>structural arrangements</u>

_______________________________________

<h2>properties of daimond: </h2><h3>appearance: transparent</h3><h3>hardness: very hard</h3><h3>thermal conductivity :very poor</h3><h3>electric conductivity: poor</h3><h3>density:</h3>

$3510 {kgm}^{3}$

<h3>uses: jewellery and drilling</h3>

_______________________________________

<h2>properties of graphite:</h2>

<h3>appearance: black shiny</h3><h3>hardness: soft ,slippery to touch</h3><h3>thermal conductivity : moderate</h3><h3>electric conductivity: good</h3><h3>density:</h3>

$2250 {kgm}^{3}$

<h3>uses:dry cell, electric arc, pencil lead, lubricant</h3>

_______________________________________

<h2>How Diamond and Graphite are chemically identical?</h2>

On heating diamond or graphite in the air, they burn completely to form carbon dioxide.
- Equal quantities of diamond and graphite when burned, produce exactly the same amount of carbon dioxide.

_______________________________________

<h2>Why the physical properties of diamond and graphite are so different?</h2>

Due to the difference in the arrangement of carbon atoms in diamond and graphite

_______________________________________

<h2><em><u>hope</u></em><em><u> it</u></em><em><u> helps</u></em><em><u> you</u></em><em><u><</u></em><em><u>3</u></em></h2>

7 0

2 years ago