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Kryger [21]
3 years ago
5

In 1676, Robert Plot discovered a large bone in a quarry in Cornwall, England. He observed that the bone looked similar to a hum

an femur, but it was much
too large. Plot did not know what to make of this new discovery and thought it was possibly from an elephant. Many years later, in 1815, William Buckland
located fossils similar to the one Robert Plot discovered. Buckland named these fossils Megalosaurus, meaning large lizard, based on the jawbones and teeth
he observed. Buckland's discoveries were the first scientific evidence that dinosaurs existed in the past.
How did this new evidence change how scientists viewed organisms from the past?
Chemistry
1 answer:
sergeinik [125]3 years ago
4 0

Answer:

D

Explanation:

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A positively charged substance is brought near the ion. What will most likely happen and why
d1i1m1o1n [39]

<u>Answer:</u> It repels positive ion and attracts negative ion.

<u>Explanation:</u>

There are 2 types of ions:

1. Cations: These ions are positively charged ions which are formed when a substance looses electrons.

2. Anions: These ions are negatively charged ions which are formed when a substance gains electrons.

It is known that, like charges repel each other and unlike charges attract each other.

As, it is given that the substance is positively charged, so it will attract anion and repel cation.

4 0
4 years ago
A runner wants to run 11.7 km. Her running pace is 8.0 mi/hr. How many minutes must she run?
ArbitrLikvidat [17]

Answer:

8 mi = 12.875 km

12.875 /60 m

= 0.21458 km / min

11.7 / 0.21458 = 54.52 min

5 0
2 years ago
Your amplifier is playing a 200 Hz tone. When you double the amplitude(loudness), what happens to the speed of the sound (v) and
kherson [118]
Its d. Speed (v) and frequency(f) both stay the same.

<span>Because Amplitude does not affect wave frequency. When you put more energy into the wave (larger amplitude) it does not affect how often you repeat a cycle. 
</span>Also speed can be altered when the medium changes through which it travels.
8 0
3 years ago
What volume of 0.235 M H2SO4 is needed to titrate 40.0 mL of 0.0500 M Na2CO M NaCO3 solution?
Andreyy89

Answer: The volume of 0.235 M H_2SO_4 needed to titrate 40.0 mL of 0.0500 M Na_2CO_3 is 8.51 ml

Explanation:

To calculate the volume of acid, we use the equation given by neutralization reaction:

n_1M_1V_1=n_2M_2V_2

where,

n_1,M_1\text{ and }V_1 are the n-factor, molarity and volume of acid which is H_2SO_4

n_2,M_2\text{ and }V_2 are the n-factor, molarity and volume of base which is Na_2CO_3

We are given:

n_1=2\\M_1=0.235M\\V_1=?mL\\n_2=2\\M_2=0.0500M\\V_2=40.0mL

Putting values in above equation, we get:

2\times 0.235\times V_1=2\times 0.0500\times 40.0\\\\V_1=8.51mL

Thus volume of 0.235 M H_2SO_4 needed to titrate 40.0 mL of 0.0500 M Na_2CO_3 is 8.51 ml

5 0
3 years ago
A 25.0 ml sample of a 0.2900 m solution of aqueous trimethylamine is titrated with a 0.3625 m solution of hcl. calculate the ph
Flauer [41]
a) After adding 10 mL of HCl

first, we need to get moles of (CH3)3N = molarity * volume

                                                                 = 0.29 m * 0.025 L
                                                                 = 0.00725M moles
then, we need to get moles of HCl = molarity * volume

                                                          = 0.3625 m * 0.01L
                                                          = 0.003625 moles

so moles of (CH3)3N remaining    = moles of (CH3)3N - moles of HCl
                                                         = 0.00725 - 0.003625

                                                      = 0.003625 moles

and when the total volume = 0.01 L + 0.025L = 0.035 L

∴ [(CH3)3N] = moles remaining / total volume

                    = 0.003625 moles / 0.035L
                    = 0.104 M

when we have Pkb so we can get Kb :

pKb = - ㏒Kb
4.19 = -㏒Kb

∴Kb = 6.5 x 10^-5

when Kb = [(CH3)3NH+] [OH-] / [(CH3)3N]

and by using ICE table we assume we have:

[(CH3)3NH+] = X & [OH] = X 

and [(CH3)3N] = 0.104 -X

by substitution:

∴ 6.5 x 10^-5 = X^2 / (0.104-X)  by solving for X

∴X = 0.00257 M
∴[OH-] = X = 0.00257 M

∴POH = -㏒[OH]

           = -㏒0.00257
           = 2.5

∴ PH = 14 - POH
         = 14 - 2.5
         = 11.5
b) after adding 20ML of HCL:

moles of HCl = molarity * volume
                       = 0.3625 m * 0.02 L

                       = 0.00725 moles

  

the complete neutralizes of (CH3)3N we make 0.003625 moles of (CH3)3NH+ So, now we need the Ka value of (CH3)3NH+:

and when the total volume = 0.02L + 0.025 = 0.045L

∴ [ (CH3)3NH+] = moles / total volume

                          = 0.003625 / 0.045L
                          = 0.08 M
 
when Ka = Kw / Kb 

and we have Kb = 6.5 x 10^-5 & we know that Kw = 1 x 10^-14 

so, by substitution:

Ka = (1 x 10^-14) / (6.5 x 10^-5)

    = 1.5 x 10^-10


when Ka expression = [(CH3)3N][H+] / [(CH3)3NH+]

by substitution:

∴ 1.5 x 10^-10 = X^2 / (0.08 - X)  by solving for X

∴X = 3.5 x 10^-6  M

∴ [H+]= X = 3.5 x 10^-6 M

∴PH = -㏒[H+]

        = -㏒(3.5 x 10^-6)

       = 5.5


C) after adding 30ML of HCl:

moles of HCl = molarity * volume 

                       = 0.3625m * 0.03L

                       = 0.011 moles

and when moles of (CH3)3N neutralized = 0.003625 moles 

∴ moles of HCl remaining    = moles HCl - moles (CH3)3N neutralized

                                                = 0.011moles - 0.003625moles

                                                = 0.007375 moles
when total volume = 0.025L + 0.03L

                                = 0.055L

∴[H+] = moles / total volume

           = 0.007375 mol / 0.055L

            = 0.134 M

∴PH = -㏒[H+]

        = -㏒ 0.134

        = 0.87
8 0
3 years ago
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