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3 years ago

Read the speedometer and report the speed to the proper

Chemistry

1 answer:

Dmitry [639]3 years ago

3 0

Answer:

In miles per hour: 82 mph

In km/h: 121 km/h

Explanation:

The correct number of digits to report a measure include every certain digit plus one uncertain digit.

The speedometer has marks for:

every 2 km per hour, km/h. Because each small tick mark on the outer circle represents 2 mph.

every 10 miles per hour mph. Because each small tick mark on the inner scale represents 10 mph.

As a rule you can appreciate up to half way between two small tick marks.

So, for km/h you can appreciate half of 2 km/h, i.e. 1 km/h.

The needle is marking between 120 km/h and 122 km/h, which means that the correct measure is 121 km, where the two leftmost digits are certain and the ones digit is uncertain.

For mph, you can appreciate half of 10 mph, i.e. 5 mph. A measure between 80 and 90 mph should be read as 85 mph.

Furthermore, in this last case of mph, the space between two consecutive marks is broad and equal to 10 mph but also the needle is wide, so it is difficult to appreciate less than 5 mph.

The correct measure must have two significant digits: one certain and one uncertain. So, 82 mph is as correct as 85 mph, since the 8 is certain and the next number (either 2 or 5) is uncertain.

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Bromine (Br) belongs to the halogen family. Based on the location of the halogens, how many valence electrons does bromine have?

Amanda [17]

Answer:

D. 7

Explanation:

The halogens are found in Group 7 of the Periodic Table. If Bromine is a halogen, then that means it would be found in Group 7. Also, elements in Group 7 have 7 electrons in its outer shell, Bromine would have 7 electrons in its outer shell.

3 0

3 years ago

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A cylinder of compressed gas has a volume of 350 ml and a pressure of 931 torr. What volume in Liters would the gas occupy if al

hodyreva [135]

Answer:

$0.384\ \text{L}$

Explanation:

$P_1$ = Initial pressure = 931 torr = $931\times \dfrac{101.325}{760}=124.12\ \text{kPa}$

$P_2$ = Final pressure = 113 kPa

$V_1$ = Initial volume = 350 mL

$V_2$ = Final volume

From the Boyle's law we have

$P_1V_1=P_2V_2\\\Rightarrow V_2=\dfrac{P_1V_1}{P_2}\\\Rightarrow V_2=\dfrac{124.12\times 350}{113}\\\Rightarrow V_2=384.44\ \text{mL}=0.384\ \text{L}$

The volume the gas would occupy is $0.384\ \text{L}$ .

3 0

3 years ago

Need some help, please. Explain why anions are always larger than the atoms from which they are derived, while cations are alway

ANTONII [103]

The question requires us to explain the differences in radii of neutral atoms, cations and anions.

To answer this question, we need to keep in mind that a neutral atom presents the same number of protons (positive particles) and electrons (negative particles). Another important information is that the protons are located in the nucleus of the atom, while the electrons are around the nucleus. Also, there is an electrostatic force between protons and electrons, which means that they the protons tend to attract the electrons to the nucleus.

While a neutral atom presents the same number of protons and electrons, a cation is an ion with positive charge, which means it has lost one or more electrons. In a cation, the balance between protons and electrons doesn't exist anymore: now, there is more positive than negative charge (more protons than electrons), and the overall attractive force that the protons have for the electrons is increased. As a result, the electrons stay closer to the nucleus and the radius of a cation is smaller than the neutral atom from which it was derived.

On the other side, anions present negative charge, which means they have received electrons. Similarly to cations, the balance between protons and electrons doesn't exist anymore, but in this case, there are more electrons than protons. In an anion, the overall attractive force that the protons have for the electrons is decreased. As a result, the electrons are "more free" to move and, as they are not so attracted to the nucleus, they tend to stay farther from the positive nucleus compared to the neutral atom - because of this, the radius of an anion is larger than the neutral atom from which it was derived.

3 0

1 year ago

Perform the calculation and record the answer with the correct number of significant figures.

kotykmax [81]

The question is incomplete, here is the complete question:

A. (6.5-6.10)/3.19

B. (34.123 + 9.60) / (98.7654 - 9.249)

Answer:

For A: The answer becomes 0.1

For B: The answer becomes 0.4884

Explanation:

Significant figures are defined as the figures present in a number that expresses the magnitude of a quantity to a specific degree of accuracy.

Rules for the identification of significant figures:

Digits from 1 to 9 are always significant and have infinite number of significant figures.
All non-zero numbers are always significant. For example: 664, 6.64 and 66.4 all have three significant figures.
All zeros between the integers are always significant. For example: 5018, 5.018 and 50.18 all have four significant figures.
All zeros preceding the first integers are never significant. For example: 0.00058 has two significant figures.
All zeros after the decimal point are always significant. For example: 2.500, 25.00 and 250.0 all have four significant figures.
All zeroes used solely for spacing the decimal point are not significant. For example: 10000 has one significant figure.

Rule applied for addition and subtraction:

The least precise number present after the decimal point determines the number of significant figures in the answer.

Rule applied for multiplication and division:

In case of multiplication and division, the number of significant digits is taken from the value which has least precise significant digits

For A: (6.5-6.10)/3.19

This a a problem of subtraction and division.

First, the subtraction is carried out.

$\Rightarow \frac{6.5-6.10}{3.19}=\frac{0.4}{3.19}$

Here, the least precise number after decimal was 1.

$\Rightarrow \frac{0.4}{3.19}=0.125$

Here, the least precise number of significant digit is 1. So, the answer becomes 0.1

For B: (34.123 + 9.60) / (98.7654 - 9.249)

This a a problem of subtraction, addition and division.

First, the subtraction and addition is carried out.

$\Rightarow \frac{34.123+9.60}{98.7654-9.249}=\frac{43.723}{89.5164}=\frac{43.72}{89.516}$

Here, the least precise number after decimal in addition are 2 and in subtraction are 3

$\Rightarrow \frac{43.72}{89.516}=0.48840$

Here, the least precise number of significant digit are 4. So, the answer becomes 0.4884

6 0

3 years ago

Which of the following elements has the highest electronegativity? beryllium iodine calcium nitrogen

juin [17]

Answer: Option (d) is the correct answer.

Explanation:

An atom or element which has the ability to readily gain an electron will have high electronegativity.

Both Beryllium and Calcium are alkaline earth metals and hence they are electropositive in nature.

Whereas both iodine and nitrogen are electronegative in nature. But across the period there is an increase in electronegativity and down the group there is a decrease in electronegativity.

Nitrogen belongs to period 2 and iodine belongs to the bottom of group 17. Thus, we can conclude that nitrogen is more electronegative than iodine.

8 0

3 years ago

Read 2 more answers